[automerger skipped] [RESTRICT AUTOMERGE] Make MultiClient IMMS PendingIntent IMMUTABLE am: 60b062f7 am: 7bb86a69 -s ours

am skip reason: subject contains skip directive

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/16170294

Change-Id: I48e34378a14425561edc9b3fe9b74fa26cb8c2f8