Add variable to enable/disable istio dashboard check within grafana

Closes https://repo1.dso.mil/platform-one/big-bang/apps/core/monitoring/-/issues/56

chart/values.yaml

@@ -472,7 +472,7 @@ monitoring:
   git:
     repo: https://repo1.dso.mil/platform-one/big-bang/apps/core/monitoring.git
     path: "./chart"
-    tag: "23.1.6-bb.6"
+    tag: "23.1.6-bb.7"
 
   # -- Flux reconciliation overrides specifically for the Monitoring Package
   flux: