Merge "Add FLAG_IMMUTABLE to PendingIntents" am: 0d885b9c66 am: 748574396e am: 01502d47b7

Original change: https://android-review.googlesource.com/c/platform/packages/apps/CellBroadcastReceiver/+/2230667

Change-Id: Ic0bf3b1767781930f7661ca04d795548a5ad9c08
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>