DO NOT MERGE Increase notification channel limit. am: 5664378a7c

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/22931456

Change-Id: Ie583cdcfae673d0a3422525d213da797bae7f75b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>