Merge "Disallow apps from setting a NotificationChannel as "importantConversation"" into tm-qpr-dev am: a27acd1622

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/20913704

Change-Id: If6c17bdb6bc4a133345bf8244cba1b4f02e2c97e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>