1:1 VoIP call doesn't terminate (and cannot be terminated) when user is banned

### Steps to reproduce

Element Web (A) -> Element Web (B)
- New private room created
- A invites B
- 1:1 video call initiated
- A banned B
- B was booted from the room and shown the "you were banned" message
- _But the webcam is still on and the video is still streaming_
- And B has no way to end the call, since they're not in the room any more

Element Web (A) -> Element Android (B)
- New private room
- A invited B
- 1:1 video call initiated
- A banned B
- B left the room but continued to stream the call (at least it was very obvious to the user what was happening)
- B was able to hang up and leave the call

### Outcome

#### What did you expect?
Call to terminate upon parting the room.

#### What happened instead?
Call continued!

### Operating system

Mac

### Browser information

Chrome

### URL for webapp

app.element.io

### Application version

Latest

### Homeserver

lant.uk

### Will you send logs?

No