Forward fix for: Set FLAG_IMMUTABLE flag on FirstScreenBroadcast PendingIntent. am: 89299047d7 am: 4401663f4a

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/14936503

Change-Id: I87759b61b2744db4792e46b7b0907dd3fad0e5b1