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

Remove obsolete DOMContentLoadedEventListener

See merge request gitlab-org/gitlab!54930

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

 import milestones from '~/pages/milestones/shared';
 import initMilestonesShow from '~/pages/milestones/shared/init_milestones_show';
 
-document.addEventListener('DOMContentLoaded', () => {
-  initMilestonesShow();
-  milestones();
-});
+initMilestonesShow();
+milestones();