Fix stuck notifications

Don't tell listeners about changes to enqueued notifications;
they'll pick up the changes in the post notification runnable.

Change-Id: I56c4ba79bcf42c30ad9a0da936eb0b774a6f3f08
Merged-In: I56c4ba79bcf42c30ad9a0da936eb0b774a6f3f08
Fixes: 74236718
Test: runtest systemui-notification