Merge branch 'jnnkl-eventlistener-env-show' into 'master'

Remove obsolete DOMContentLoadedEventListener

See merge request gitlab-org/gitlab!53869

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

 import initShowEnvironment from '~/environments/mount_show';
 
-document.addEventListener('DOMContentLoaded', initShowEnvironment);
+initShowEnvironment();