Stuck notification after redacting thread root

### Steps to reproduce

* Let user A start a thread by sending a thread reply
* Let user A redact the reply
* Look at the main timeline as user B

### Outcome

#### What did you expect?

No stuck rageshake.

#### What happened instead?

See attached rageshake. I could not find a thread to mark as read in the threads list, but the notification dot says there should be one.

### Operating system

Windows 11

### Application version

Element Nightly version: 0.0.1-nightly.2023053001 Olm version: 3.2.14

### How did you install the app?

The Internet

### Homeserver

t2l.io

### Will you send logs?

Yes