[2/n] Remove use of `persist.wm.debug.desktop_mode_2`

`persist.wm.debug.desktop_mode_2` is no longer needed as desktop
windowing now uses a runtime flag which can be modified using the command: `adb shell device_config put lse_desktop_experience
com.android.window.flags.enable_desktop_windowing_mode (true/false)`.

Flag: NONE
Fixes: 326060855
Bug: 304778354
Test: build & `adb shell device_config put lse_desktop_experience
com.android.window.flags.enable_desktop_windowing_mode true && adb
reboot` desktop windowing mode should be enabled.

Change-Id: I25d509c0912ab3266a32ad992333460332b8b0a2
diff --git a/src/com/android/launcher3/Launcher.java b/src/com/android/launcher3/Launcher.java
index d6312c3..b0a1bd4 100644
--- a/src/com/android/launcher3/Launcher.java
+++ b/src/com/android/launcher3/Launcher.java
@@ -318,9 +318,6 @@
     private static final FloatProperty<Hotseat> HOTSEAT_WIDGET_SCALE =
             HOTSEAT_SCALE_PROPERTY_FACTORY.get(SCALE_INDEX_WIDGET_TRANSITION);
 
-    private static final boolean DESKTOP_MODE_SUPPORTED =
-            "1".equals(Utilities.getSystemProperty("persist.wm.debug.desktop_mode_2", "0"));
-
     private final ModelCallbacks mModelCallbacks = createModelCallbacks();
 
     private final KeyboardShortcutsDelegate mKeyboardShortcutsDelegate =
@@ -2713,8 +2710,7 @@
     }
 
     private void updateDisallowBack() {
-        // TODO(b/304778354): remove sysprop once desktop aconfig flag supports dynamic overriding
-        if (Flags.enableDesktopWindowingMode() || DESKTOP_MODE_SUPPORTED) {
+        if (Flags.enableDesktopWindowingMode()) {
             // Do not disable back in launcher when prototype behavior is enabled
             return;
         }