Active VC participants don't show up automatically with Sliding Sync enabled

[cyrneko]

Describe the bug

When Sliding Sync is enabled, VC participants do not show up until that channel is manually selected at least once.

Reproduction

No response

Expected behavior

No response

Platform and versions

- OS: Linux x86_64
- Browser: Mozilla/5.0 (X11; Linux x86_64; rv:140.0) Gecko/20100101 Firefox/140.0
- Sable: v1.20.0 (12e5547)

Additional context

No response