Add AMBIENT_WALLPAPER to shell permissions

A wallpaper supporting ambient mode is required to check that WallpaperService#onAmbientModeChanged is called by the main thread.

Bug: 240112941
Test: atest CtsWallpaperTestcases
Change-Id: I6f7c36717366edd84802a58184798f72f2fea5cd
diff --git a/packages/Shell/AndroidManifest.xml b/packages/Shell/AndroidManifest.xml
index 90fab08..3d7a959 100644
--- a/packages/Shell/AndroidManifest.xml
+++ b/packages/Shell/AndroidManifest.xml
@@ -360,6 +360,9 @@
     <!-- Permission needed to test wallpaper dimming -->
     <uses-permission android:name="android.permission.SET_WALLPAPER_DIM_AMOUNT" />
 
+    <!-- Permission needed to test wallpapers supporting ambient mode -->
+    <uses-permission android:name="android.permission.AMBIENT_WALLPAPER" />
+
     <!-- Permission required to test ContentResolver caching. -->
     <uses-permission android:name="android.permission.CACHE_CONTENT" />