Stuck notification in DM

### Steps to reproduce

unclear.

there's a thread where i wrote the last reply

### Outcome

#### What did you expect?
no unreads

(or at least the thread wrongly causing the unread should be shown as such)

#### What happened instead?
room has 1 unread according to room list. there are no new messages. there are no unread markers on the thread lists toggle nor on the individual threads.

### Operating system

arch

### Browser information

firefox

### URL for webapp

develop.element.io

### Application version

Element version: fcd805255c26-react-64f762d7b0f3-js-5788d9744b76 Olm version: 3.2.14

### Homeserver

matrix.org

### Will you send logs?

Yes