[automerger skipped] [DO NOT MERGE] Make screenshot error notification PendingIntent immutable am: 1eecc874b6 am: cc526dd833 -s ours

am skip reason: subject contains skip directive

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/13519315

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I46b1a2f5712e55dff7d27301167026ec784ad7f1