Avatar update surfaces room due to activity

### Steps to reproduce

When a contact updates their avatar, the room with that user is marked as having new activity. This can be bothersome when you have old chats surfaced due to only an avatar change.

### Outcome

#### What did you expect?
When a contact updates their avatar, the room isn't marked as having new activity.

#### What happened instead?
When a contact updates their avatar, the room is marked as having unread activity and is pushed to the top if the category sort is by activity.

### Operating system

Windows

### Application version

Element version: 1.11.61 Crypto version: Olm 3.2.15

### How did you install the app?

https://element.io/download

### Homeserver

synapse 1.103.0+focal1

### Will you send logs?

Yes

The issue provides no source file, test, or entry point. Reproduce the avatar update on Windows with Element 1.11.61, checking whether the affected room gains unread activity or moves to the top when sorted by activity; done means the avatar change no longer causes either behavior.

Written by the indexing model from the issue text.