Mark testNotificationEvent_quotaBump as flaky. am: 33cecbe1 am: 52a15269 am: 6b26a0d7 am: 067f3818

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/25631212



Change-Id: I0c614acb59682af129de654b84d81a0c023e83b5
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>