Kick reason is sometimes absent for federated calls

### Steps to reproduce

1. Set up an Element Web to allow guest links
2. Create a public room & start a video call in it
3. Copy the guest join URL and have a guest join it (unsure if the guest needs to be on a different homeserver)
4. Use that link to join the call
5. Have the creator of the room kick the joined user with a reason

### Outcome

#### What did you expect?
The Element Call SPA for the guest user should show the kick reason, like so:


This does happen when the room the guest is kicked from is a knock-access room or a public video room.

#### What happened instead?
No kick reason is shown:


### Operating system

Fedora

### Browser information

Firefox version 125

### URL for webapp

Development version (5284479e)

### Will you send logs?

No

Reproduce the issue in the Element Call SPA using the guest-link flow described, comparing a public room with a knock-access room and checking whether the guest is on another homeserver. Trace how the kick reason is received and displayed for federated calls; done means the guest sees the creator's reason consistently.

Written by the indexing model from the issue text.