Correct vulnerability when setting pending intents on import/export notifications by setting FLAG_IMMUTABLE am: 1d595f80e9 am: 835bc188db am: 2aedd25d2e am: b19ebd07e3

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Contacts/+/12272170

Change-Id: I514dae68f341d57057e720a7063601db1c071c2e