Merge branch '12151-instance-level-clusters-cluster-health-not-displaying' into 'master'

Resolve "Instance level clusters > Cluster health not displaying"

Closes #12151

See merge request gitlab-org/gitlab-ee!14440

ee/app/assets/javascripts/pages/admin/clusters/show/index.js

+import initClusterHealth from '../../../projects/clusters/show/cluster_health';
+
+document.addEventListener('DOMContentLoaded', initClusterHealth);

ee/changelogs/unreleased/12151-instance-level-clusters-cluster-health-not-displaying.yml

+---
+title: Fix cluster health charts on instance level
+merge_request: 14440
+author:
+type: fixed