Banning a user and removing their messages should hide / remove their username / display name from the timelime

### Steps to reproduce

1. wait for spammer to join a room
2. ban spammer
3. use "remove recent messages" to remove their most recent messages

In my case I used "remove recent messages" twice, since I didn't know how it worked yet. First without removing events or what the option was called, then again with.

### Outcome

#### What did you expect?

I expected all traces of the spammer to disappear from the room, *including* their nick and avatar.

#### What happened instead?

In both element and nheko I can still see their message events, but the events are listed as "Message deleted by ". Their avatar is hidden after a manual clean of the cache (which shouldn't be necessary imo).

But their nick / display name is still being shown, which can be set by spammers to... spam.

Please excuse me if there's already an issue ticket for this or a more fitting repo, I couldn't find one.

### Operating system

_No response_

### Application version

Element version: 1.11.44 Olm version: 3.2.14

### How did you install the app?

_No response_

### Homeserver

_No response_

### Will you send logs?

No

The report concerns the room timeline in Element and nheko; no repository file, test, or entry point is named. Start by reproducing the ban and “remove recent messages” sequence in a room, then investigate where deleted events still obtain the sender nick or display name. Done means the deleted user's username, display name, and avatar no longer remain visible after cleanup.

Written by the indexing model from the issue text.