[automerger skipped] Set FLAG_IMMUTABLE flag on FirstScreenBroadcast PendingIntent. am: 6a7a7f6bad am: 3c3e3e0737 am: 5785789dc3 am: 1d41f93c37 am: d997f9957d -s ours

am skip reason: Merged-In I8d8e38a1aa6bdf13879d460cfa84cabe6c6bb1f2 with SHA-1 6a7a7f6bad is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/14651127

Change-Id: I6f44a01322735d30bc3d8318e0d625968a4fd363