Remove DOMContentLoaded Eventlisteners

Removing DOMContentLoaded Eventlisteners from
index files since the scripts
are embedded using the defer tag.

ee/app/assets/javascripts/pages/projects/dependencies/index/index.js

 import initDependenciesApp from 'ee/dependencies';
 
-document.addEventListener('DOMContentLoaded', initDependenciesApp);
+initDependenciesApp();

ee/app/assets/javascripts/pages/projects/merge_requests/conflicts/index.js

 import initSidebarBundle from 'ee/sidebar/sidebar_bundle';
 import initMergeConflicts from '~/merge_conflicts/merge_conflicts_bundle';
 
-document.addEventListener('DOMContentLoaded', () => {
-  initSidebarBundle();
-  initMergeConflicts();
-});
+initSidebarBundle();
+initMergeConflicts();

ee/app/assets/javascripts/pages/projects/merge_requests/creations/new/index.js

@@ -2,7 +2,6 @@ import '~/pages/projects/merge_requests/creations/new/index';
 import UserCallout from '~/user_callout';
 import initForm from '../../shared/init_form';
 
-document.addEventListener('DOMContentLoaded', () => {
-  initForm();
-  return new UserCallout();
-});
+initForm();
+// eslint-disable-next-line no-new
+new UserCallout();

ee/app/assets/javascripts/pages/projects/merge_requests/edit/index.js

 import '~/pages/projects/merge_requests/edit/index';
 import initForm from '../shared/init_form';
 
-document.addEventListener('DOMContentLoaded', initForm);
+initForm();

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

 import '~/pages/projects/show/index';
 import initVueAlerts from '~/vue_alerts';
 
-document.addEventListener('DOMContentLoaded', () => {
-  initVueAlerts();
-});
+initVueAlerts();

ee/app/assets/javascripts/pages/trials/namespace_select.js

 import $ from 'jquery';
 
-document.addEventListener('DOMContentLoaded', () => {
-  const namespaceId = $('#namespace_id');
-  const newGroupName = $('#group_name');
+const namespaceId = $('#namespace_id');
+const newGroupName = $('#group_name');
 
-  namespaceId.on('change', () => {
+namespaceId.on('change', () => {
   const enableNewGroupName = namespaceId.val() === '0';
 
   newGroupName
     .toggleClass('hidden', !enableNewGroupName)
     .find('input')
     .prop('required', enableNewGroupName);
-  });
-
-  namespaceId.trigger('change');
 });
+
+namespaceId.trigger('change');