update "number of subscribers" immediately (not on refresh)

Repro steps:
1. Find a chat with a tag you are subscribed to
2. Hover over the tag at the top of the chat window
3. Click Unsubscribe

Expected: Number of subscribers should go down by 1
Actual: Number of subscribers stays the same

This issue also exists in reverse. When you subscribe to a tag, the count does not go up.