Remove DOMContentLoaded Eventlisteners

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

app/assets/javascripts/pages/groups/clusters/destroy/index.js

 import ClustersBundle from '~/clusters/clusters_bundle';
 
-document.addEventListener('DOMContentLoaded', () => {
-  new ClustersBundle(); // eslint-disable-line no-new
-});
+new ClustersBundle(); // eslint-disable-line no-new

app/assets/javascripts/pages/groups/clusters/edit/index.js

 import ClustersBundle from '~/clusters/clusters_bundle';
 
-document.addEventListener('DOMContentLoaded', () => {
-  new ClustersBundle(); // eslint-disable-line no-new
-});
+new ClustersBundle(); // eslint-disable-line no-new

app/assets/javascripts/pages/groups/clusters/index.js

 import initCreateCluster from '~/create_cluster/init_create_cluster';
 import initIntegrationForm from '~/clusters/forms/show/index';
 
-document.addEventListener('DOMContentLoaded', () => {
-  initCreateCluster(document, gon);
-  initIntegrationForm();
-});
+initCreateCluster(document, gon);
+initIntegrationForm();

app/assets/javascripts/pages/groups/clusters/index/index.js

 import PersistentUserCallout from '~/persistent_user_callout';
 import initClustersListApp from '~/clusters_list';
 
-document.addEventListener('DOMContentLoaded', () => {
-  const callout = document.querySelector('.gcp-signup-offer');
-  PersistentUserCallout.factory(callout);
-  initClustersListApp();
-});
+const callout = document.querySelector('.gcp-signup-offer');
+PersistentUserCallout.factory(callout);
+initClustersListApp();

app/assets/javascripts/pages/groups/clusters/new/index.js

 import initNewCluster from '~/clusters/new_cluster';
 
-document.addEventListener('DOMContentLoaded', () => {
-  initNewCluster();
-});
+initNewCluster();

app/assets/javascripts/pages/groups/clusters/show/index.js

 import ClustersBundle from '~/clusters/clusters_bundle';
 import initClusterHealth from '~/pages/projects/clusters/show/cluster_health';
 
-document.addEventListener('DOMContentLoaded', () => {
-  new ClustersBundle(); // eslint-disable-line no-new
-  initClusterHealth();
-});
+new ClustersBundle(); // eslint-disable-line no-new
+initClusterHealth();