Ref T4900. When a card is edited, we currently emit an update notification for all the projects the task is tagged with. This isn't quite the right set:
- We want to emit notifications for projects the task was previously tagged with, so it can be removed from boards it should no longer be part of.
- We want to emit notifications for ancestors of projects the task is or was tagged with, so parent project boards can be updated.
- However, we don't need to emit notifications for projects that don't actually have workboards.
Adjust the notification set to align better to these rules.