Remove DOMContentLoaded Eventlisteners

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

ee/app/assets/javascripts/pages/groups/analytics/merge_request_analytics/index.js

 import initMergeRequestAnalyticsApp from 'ee/analytics/merge_request_analytics';
 
-document.addEventListener('DOMContentLoaded', initMergeRequestAnalyticsApp);
+initMergeRequestAnalyticsApp();

ee/app/assets/javascripts/pages/groups/analytics/productivity_analytics/index.js

 import initProductivityAnalyticsApp from 'ee/analytics/productivity_analytics';
 
-document.addEventListener('DOMContentLoaded', () => {
-  initProductivityAnalyticsApp();
-});
+initProductivityAnalyticsApp();

ee/app/assets/javascripts/pages/groups/analytics/repository_analytics/index.js

 import initRepositoryAnalyticsApp from 'ee/analytics/repository_analytics';
 
-document.addEventListener('DOMContentLoaded', () => {
-  initRepositoryAnalyticsApp();
-});
+initRepositoryAnalyticsApp();

ee/app/assets/javascripts/pages/groups/epics/index/index.js

@@ -5,17 +5,15 @@ import issuableInitBulkUpdateSidebar from '~/issuable_init_bulk_update_sidebar';
 
 const EPIC_BULK_UPDATE_PREFIX = 'epic_';
 
-document.addEventListener('DOMContentLoaded', () => {
-  initFilteredSearch({
+initFilteredSearch({
   page: 'epics',
   isGroup: true,
   isGroupDecendent: true,
   useDefaultState: true,
   filteredSearchTokenKeys: FilteredSearchTokenKeysEpics,
   stateFiltersSelector: '.epics-state-filters',
-  });
+});
 
-  initEpicCreateApp(true);
+initEpicCreateApp(true);
 
-  issuableInitBulkUpdateSidebar.init(EPIC_BULK_UPDATE_PREFIX);
-});
+issuableInitBulkUpdateSidebar.init(EPIC_BULK_UPDATE_PREFIX);