Remove unused AssistantThreadFeedback event (#27021)

It looks like:

- https://github.com/zed-industries/zed/pull/26780

accidentally added a new event type, `AssistantThreadFeedback`, using
the old event system, that it didn't end up actually using, as the code
actually relies on using the newer (preferred) `telemetry::event!()`.

Release Notes:

- N/A
ed510b5e93Joseph T. Lyons committed on 3/18/2025, 8:39:54 PM· committed by GitHubparent674c572
2 files changedLine totals unavailable