Message Editing: Update notifications

We should update notifications with updated messages but there are several use cases which can be related:
- the edited message is still displayed in a notification
- the notification for the edited message is no more displayed
- the edit does not trigger a notification anymore
- the edit triggers a notif while the original message did not

The issue names no files, tests, or entry points. Reproduce each listed message-edit and notification case in the iOS app, then define the expected behavior for every case before locating the notification and message-editing code; done means edited-message notifications consistently follow those decisions.

Written by the indexing model from the issue text.