Finish parent activities only in setting wallpaper am: b5e9bd7ea8 am: a4b8153a9b

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/WallpaperPicker2/+/11862087

Change-Id: I48e82e35240b7a5fac7617e326ccd597162ea71a