Correct vulnerability when setting pending intents on import/export notifications by setting FLAG_IMMUTABLE am: 1d595f80e9 am: 835bc188db am: 2aedd25d2e am: b19ebd07e3 am: f24d838e03

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

Change-Id: Ia2119d1e7f02448c2ddda7a24585d22e30bc91d3