changelog: re-add removed to unreleased changes

This heading went missing somewhere along the line, but DEVELOPMENT.md
points out that we should have it.

Author: LawnGnome

CHANGELOG.md

@@ -17,6 +17,8 @@ All notable changes to `src-cli` are documented in this file.
 
 ### Fixed
 
+### Removed
+
 ## 3.21.6
 
 ### Fixed