Enable iteration resource change event tracking

This sets the feature flag to be enabled by default. Instead of system
notes, event records would be created in the backend.

ee/app/services/ee/issuable/common_system_notes_service.rb

@@ -64,7 +64,7 @@ module EE
       end
 
       def iteration_changes_tracking_enabled?
-        ::Feature.enabled?(:track_iteration_change_events, issuable.project)
+        ::Feature.enabled?(:track_iteration_change_events, issuable.project, default_enabled: true)
       end
     end
   end

ee/changelogs/unreleased/enable-tracking-iteration-events-ff.yml

+---
+title: Track iteraton changes using resource events
+merge_request: 40841
+author:
+type: other