Update addons.sample.yaml with correct namespace for kubernetes-dashboard (#1243)

bootstrap/vars/addons.sample.yaml

@@ -20,7 +20,7 @@ addon_kube_prometheus_stack:
 addon_kubernetes_dashboard:
   enabled: false
   # NOTE: Password can be obtained by running the following command once it is deployed:
-  #   kubectl -n monitoring get secret kubernetes-dashboard -o jsonpath='{.data.token}' | base64 -d
+  #   kubectl -n observability get secret kubernetes-dashboard -o jsonpath='{.data.token}' | base64 -d
 
 # https://github.com/weaveworks/weave-gitops
 addon_weave_gitops: