Clean up fully rolled out HeadlessDeviceOwnerSingleUserEnabled

Flag was rolled out in Android V. Keeping flag definition since it is
exported.

Bug: 335663055
Test: TH
Flag: EXEMPT flag cleanup
Change-Id: I6fcecf1f4d6ae834afcd21cf5861bda609078bf0
diff --git a/core/api/current.txt b/core/api/current.txt
index 861be40..6cbb9fa 100644
--- a/core/api/current.txt
+++ b/core/api/current.txt
@@ -7875,7 +7875,7 @@
     method public void writeToParcel(android.os.Parcel, int);
     field @NonNull public static final android.os.Parcelable.Creator<android.app.admin.DeviceAdminInfo> CREATOR;
     field public static final int HEADLESS_DEVICE_OWNER_MODE_AFFILIATED = 1; // 0x1
-    field @FlaggedApi("android.app.admin.flags.headless_device_owner_single_user_enabled") public static final int HEADLESS_DEVICE_OWNER_MODE_SINGLE_USER = 2; // 0x2
+    field public static final int HEADLESS_DEVICE_OWNER_MODE_SINGLE_USER = 2; // 0x2
     field public static final int HEADLESS_DEVICE_OWNER_MODE_UNSUPPORTED = 0; // 0x0
     field public static final int USES_ENCRYPTED_STORAGE = 7; // 0x7
     field public static final int USES_POLICY_DISABLE_CAMERA = 8; // 0x8
diff --git a/core/api/system-current.txt b/core/api/system-current.txt
index e1e63cc..1993d0e 100644
--- a/core/api/system-current.txt
+++ b/core/api/system-current.txt
@@ -1422,7 +1422,7 @@
     field public static final int STATUS_DEVICE_ADMIN_NOT_SUPPORTED = 13; // 0xd
     field public static final int STATUS_HAS_DEVICE_OWNER = 1; // 0x1
     field public static final int STATUS_HAS_PAIRED = 8; // 0x8
-    field @FlaggedApi("android.app.admin.flags.headless_device_owner_single_user_enabled") public static final int STATUS_HEADLESS_ONLY_SYSTEM_USER = 17; // 0x11
+    field public static final int STATUS_HEADLESS_ONLY_SYSTEM_USER = 17; // 0x11
     field public static final int STATUS_HEADLESS_SYSTEM_USER_MODE_NOT_SUPPORTED = 16; // 0x10
     field public static final int STATUS_MANAGED_USERS_NOT_SUPPORTED = 9; // 0x9
     field public static final int STATUS_NONSYSTEM_USER_EXISTS = 5; // 0x5
diff --git a/core/java/android/app/admin/DeviceAdminInfo.java b/core/java/android/app/admin/DeviceAdminInfo.java
index 46c9e78..4f2efa4 100644
--- a/core/java/android/app/admin/DeviceAdminInfo.java
+++ b/core/java/android/app/admin/DeviceAdminInfo.java
@@ -16,9 +16,6 @@
 
 package android.app.admin;
 
-import static android.app.admin.flags.Flags.FLAG_HEADLESS_DEVICE_OWNER_SINGLE_USER_ENABLED;
-
-import android.annotation.FlaggedApi;
 import android.annotation.IntDef;
 import android.annotation.NonNull;
 import android.app.admin.flags.Flags;
@@ -195,7 +192,6 @@
      * DPCs should set the value of attribute "headless-device-owner-mode" inside the
      * "headless-system-user" tag as "single_user".
      */
-    @FlaggedApi(FLAG_HEADLESS_DEVICE_OWNER_SINGLE_USER_ENABLED)
     public static final int HEADLESS_DEVICE_OWNER_MODE_SINGLE_USER = 2;
 
     /**
diff --git a/core/java/android/app/admin/DevicePolicyManager.java b/core/java/android/app/admin/DevicePolicyManager.java
index 5088ea6..0fc77f0 100644
--- a/core/java/android/app/admin/DevicePolicyManager.java
+++ b/core/java/android/app/admin/DevicePolicyManager.java
@@ -59,7 +59,6 @@
 import static android.app.admin.flags.Flags.FLAG_ESIM_MANAGEMENT_ENABLED;
 import static android.app.admin.flags.Flags.FLAG_DEVICE_POLICY_SIZE_TRACKING_ENABLED;
 import static android.app.admin.flags.Flags.FLAG_HEADLESS_DEVICE_OWNER_PROVISIONING_FIX_ENABLED;
-import static android.app.admin.flags.Flags.FLAG_HEADLESS_DEVICE_OWNER_SINGLE_USER_ENABLED;
 import static android.app.admin.flags.Flags.onboardingBugreportV2Enabled;
 import static android.app.admin.flags.Flags.onboardingConsentlessBugreports;
 import static android.app.admin.flags.Flags.FLAG_IS_MTE_POLICY_ENFORCED;
@@ -2988,7 +2987,6 @@
      * @hide
      */
     @SystemApi
-    @FlaggedApi(FLAG_HEADLESS_DEVICE_OWNER_SINGLE_USER_ENABLED)
     public static final int STATUS_HEADLESS_ONLY_SYSTEM_USER = 17;
 
     /**
diff --git a/core/java/android/app/admin/flags/flags.aconfig b/core/java/android/app/admin/flags/flags.aconfig
index fe7b482..f2861fe 100644
--- a/core/java/android/app/admin/flags/flags.aconfig
+++ b/core/java/android/app/admin/flags/flags.aconfig
@@ -173,6 +173,7 @@
   bug: "295301164"
 }
 
+# Fully rolled out and must not be used.
 flag {
   name: "headless_device_owner_single_user_enabled"
   is_exported: true
diff --git a/services/devicepolicy/java/com/android/server/devicepolicy/DevicePolicyManagerService.java b/services/devicepolicy/java/com/android/server/devicepolicy/DevicePolicyManagerService.java
index a9bf212..af4a48d 100644
--- a/services/devicepolicy/java/com/android/server/devicepolicy/DevicePolicyManagerService.java
+++ b/services/devicepolicy/java/com/android/server/devicepolicy/DevicePolicyManagerService.java
@@ -12680,14 +12680,12 @@
         Preconditions.checkCallAuthorization(isDefaultDeviceOwner(caller));
         checkCanExecuteOrThrowUnsafe(DevicePolicyManager.OPERATION_CREATE_AND_MANAGE_USER);
 
-        if (Flags.headlessDeviceOwnerSingleUserEnabled()) {
-            // Block this method if the device is in headless main user mode
-            Preconditions.checkCallAuthorization(
-                    !mInjector.userManagerIsHeadlessSystemUserMode()
-                            || getHeadlessDeviceOwnerModeForDeviceOwner()
-                            != HEADLESS_DEVICE_OWNER_MODE_SINGLE_USER,
-                    "createAndManageUser was called while in headless single user mode");
-        }
+        // Block this method if the device is in headless main user mode
+        Preconditions.checkCallAuthorization(
+                !mInjector.userManagerIsHeadlessSystemUserMode()
+                        || getHeadlessDeviceOwnerModeForDeviceOwner()
+                        != HEADLESS_DEVICE_OWNER_MODE_SINGLE_USER,
+                "createAndManageUser was called while in headless single user mode");
 
         // Only allow the system user to use this method
         Preconditions.checkCallAuthorization(caller.getUserHandle().isSystem(),
@@ -17313,7 +17311,7 @@
                     return STATUS_HEADLESS_SYSTEM_USER_MODE_NOT_SUPPORTED;
                 }
 
-                if (Flags.headlessDeviceOwnerSingleUserEnabled() && isHeadlessModeSingleUser) {
+                if (isHeadlessModeSingleUser) {
                     ensureSetUpUser = mUserManagerInternal.getMainUserId();
                     if (ensureSetUpUser == UserHandle.USER_NULL) {
                         return STATUS_HEADLESS_ONLY_SYSTEM_USER;
@@ -22061,8 +22059,8 @@
             setTimeAndTimezone(provisioningParams.getTimeZone(), provisioningParams.getLocalTime());
             setLocale(provisioningParams.getLocale());
 
-            int deviceOwnerUserId = Flags.headlessDeviceOwnerSingleUserEnabled()
-                    && isSingleUserMode && mInjector.userManagerIsHeadlessSystemUserMode()
+            int deviceOwnerUserId =
+                    isSingleUserMode && mInjector.userManagerIsHeadlessSystemUserMode()
                     ? mUserManagerInternal.getMainUserId() : UserHandle.USER_SYSTEM;
 
             if (!removeNonRequiredAppsForManagedDevice(