Edit Message events are not correctly dealt with

### Steps to reproduce

I feel like there is a problem with receiving edits for other people's messages.

Steps:
1. Have another person send a message to you or a shared room
2. Let the other person edit their message

### Outcome

#### What did you expect?
To have the correct (edited) message shown in the room list as the message preview.
#### What happened instead?
- the room list shows the original message as the preview
- The notification will not get marked as read even after opening the room and reading the edited message.

See the message in the room:

See the room in the room list after opening the edited message:

### Your phone model

iPhone 8

### Operating system version

15.4

### Application version

Element 1.8.10 - but this was happening before

### Homeserver

Synapse 1.55.2

### Will you send logs?

No

No source files or tests are named. Start by reproducing the edit flow on iOS, then trace how edits from other users update the room-list preview and notification read state. Done means the edited text appears in the room list and opening the room marks the notification as read.

Written by the indexing model from the issue text.