Do not allow home screen only wallpaper if current is the default am: 7742666ea7 am: cd23f3d5f0

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/WallpaperPicker2/+/15567276

Change-Id: Ie53b9abccd8923fd4c06208b26a3c73eaa19d2a7