remove the com.android.threadnetwork from apex_available list

The ot-daemon has been moved from the com.android.threadnetwork to
com.android.tethering. No need to add the com.android.threadnetwork
to the apex_available list.

Bug: b/312573093
Test: Build
Change-Id: I2216e0d2a1d30738c405a174909d174cbc1f0bc7
diff --git a/threadnetwork/aidl/Android.bp b/threadnetwork/aidl/Android.bp
index c621b81..7e674e0 100644
--- a/threadnetwork/aidl/Android.bp
+++ b/threadnetwork/aidl/Android.bp
@@ -15,9 +15,6 @@
             apex_available: [
                 "//apex_available:platform",
                 "com.android.tethering",
-                // Keep the threadnetwork apex to make it buildable on udc-mainline-prod.
-                // TODO: remove it after moving ot-daemon into tethering.
-                "com.android.threadnetwork",
             ],
             min_sdk_version: "30",
         },