Deprecated FlutterView v1 points to FlutterView v2 (#16304)

FlutterView#enableTransparentBackground has been deprecated for some
time now since it breaks a11y highlighting in most cases. When the
warning was first added there was no known workaround, but now the v2
embedding is in stable and ready to support this usecase. Update the
warning to point to the v2 embedding.

shell/platform/android/io/flutter/view/FlutterView.java

@@ -331,11 +331,18 @@ public class FlutterView extends SurfaceView implements BinaryMessenger, Texture
      * Sets it on top of its window. The background color still needs to be
      * controlled from within the Flutter UI itself.
      *
-     * @deprecated This breaks accessibility highlighting. See https://github.com/flutter/flutter/issues/37025.
+     * @deprecated FlutterView in the v1 embedding is always a SurfaceView and will
+     *             cover accessibility highlights when transparent. Consider
+     *             migrating to the v2 Android embedding, using
+     *             {@link io.flutter.embedding.android.FlutterView.RenderMode#texture},
+     *             and setting
+     *             {@link io.flutter.embedding.android.FlutterView.TransparencyMode#transparent}.
+     *             See also
+     *             https://github.com/flutter/flutter/wiki/Upgrading-pre-1.12-Android-projects.
      */
     @Deprecated
     public void enableTransparentBackground() {
-        Log.w(TAG, "Warning: FlutterView is set on top of the window. Accessibility highlights will not be visible in the Flutter UI. https://github.com/flutter/flutter/issues/37025");
+        Log.w(TAG, "FlutterView in the v1 embedding is always a SurfaceView and will cover accessibility highlights when transparent. Consider migrating to the v2 Android embedding. https://github.com/flutter/flutter/wiki/Upgrading-pre-1.12-Android-projects");
         setZOrderOnTop(true);
         getHolder().setFormat(PixelFormat.TRANSPARENT);
     }