chore: Rename dashboard and file

Author: imusmanmalik

dashboards/cert-manager.json dashboards/overview.jsondashboards/cert-manager.json renamed to dashboards/overview.json

@@ -1226,7 +1226,7 @@
     ],
   },
   timezone: '',
-  title: 'Cert Manager',
+  title: 'Cert Manager / Overview',
   uid: 'TvuRo2iMk',
   version: 1,
 }