Message highlighted as mention, but room did not receive badge update

### Steps to reproduce

Be me? Not entirely sure. Here's what I think happened:

1. Give 3 users permission to send `@room` messages in an unencrypted room. Observe as User A.
2. As User B, send a message with `@room` in it. Mark the room as read on User A's side.
3. As User C, reply to that message *without* explicit `@room` in the reply body. The `@room` from the original message is carried through.
4. Observing as User A, note that the message is highlighted but the room is missing a red notification badge.

### Outcome

#### What did you expect?

To receive a red badge, or for the message to not be highlighted.

#### What happened instead?

Worth noting that the event *does* have an `m.mentions` thing in it:

I'm not sure I have the intentional messages feature enabled - hopefully my rageshake will indicate that.

### Operating system

Windows 11

### Application version

Element Nightly version: 0.0.1-nightly.2023112601 Crypto version: Olm 3.2.15

### How did you install the app?

The Internet

### Homeserver

t2l.io

### Will you send logs?

Yes