Merge branch 'jnnkl-remove-eventlistener-milestones-index' into 'master'

Remove obsolete DOMContentLoadedEventListener

See merge request gitlab-org/gitlab!54933

app/assets/javascripts/pages/projects/milestones/index/index.js

 import milestones from '~/pages/milestones/shared';
 
-document.addEventListener('DOMContentLoaded', milestones);
+milestones();