[automerger skipped] Revert "Set FLAG_IMMUTABLE flag on FirstScreenBroadcast...

[automerger skipped] Revert "Set FLAG_IMMUTABLE flag on FirstScreenBroadcast PendingIntent. am: 6a7a7f6b am: 3c3e3e07 am: 5785789d" am: 1aa95b84 -s ours

am skip reason: Merged-In I8d8e38a1aa6bdf13879d460cfa84cabe6c6bb1f2 with SHA-1 6a7a7f6b is already in history. Merged-In was found from reverted change.

Reverted change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/14923132

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/14920673

Change-Id: Idc27b6e16f539702cacf917fc495d04182d96703