Update to new grafana schema (#2525)

* Update to new grafana schema

* Update dashboard version

Author: Sleuth56

charts/victoria-metrics-k8s-stack/_index.md.gotmpl

@@ -160,10 +160,11 @@ grafana:
     dashboards:
       enabled: false
   dashboards:
-    vmcluster:
-      gnetId: 11176
-      revision: 38
-      datasource: VictoriaMetrics
+    default:
+      vmcluster:
+        gnetId: 11176
+        revision: 45
+        datasource: VictoriaMetrics
 ```
 When using this approach, you can find dashboards for VictoriaMetrics components published [here](https://grafana.com/orgs/victoriametrics).