Merge "Remove the fallback AddSupervisedUserActivity." into tm-dev am: 15a89a60ac

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Settings/+/20665167

Change-Id: Ie2670823d5820f75d101fc6236c8154869db88d1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>