Document query performance improvement

CHANGELOG.md

@@ -55,6 +55,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Fixed slow timelines when there are a lot of deactivated users
 - Fixed account deletion API
 - Fixed lowercase HTTP HEAD method in the Media Proxy Preview code
+- Improved performance for filtering out deactivated and invisible users
 
 ### Removed
 - Quack, the logging backend that pushes to Slack channels