Element should provide a warning that leaving a room/chat loses access to old comments previously visible

### Description

Leaving a room/chat loses access to old comments though the room/chat is kept in the Historical section of the client. The client says that it will be kept in the historical section but does not say that this will not enable comments to be seen.

### Steps to reproduce

- Leave chat
- Attempt to see historical comments from left chat

Either historical chat should be retained or a warning should be given that they will not be. The current situation suggests that they will but leaves the user to discover that they are after the fact when it is now too late.

Logs being sent: no

### Version information

- **Platform**: desktop?

For the desktop app:

- **OS**: Windows, Ubuntu
- **Version**: 1.7.23