Explain why flags are pushed for many actions

ee/app/controllers/ee/projects/pipelines_controller.rb

@@ -7,6 +7,10 @@ module EE
       extend ::Gitlab::Utils::Override
 
       prepended do
+        # Since feature flags are pushed only once on page load, we need to
+        # ensure they're pushed for all tabs in the pipelines view. This is
+        # because the user can freely navigate between them *without*
+        # triggering a page load.
         before_action only: [:show, :builds, :failures, :security, :licenses] do
           push_frontend_feature_flag(:pipeline_report_api)
         end