Merge pull request #15327 from agilgur5/1.19-release-secure-metrics-server

docs(release): add improved security of `metrics-server` note to 1.19

Author: k8s-ci-robot

docs/releases/1.19-NOTES.md

@@ -72,6 +72,7 @@ has been updated by a newer version of kOps unless it is given the `--allow-kops
 ### Addons
 
 * Metrics Server is now available as a configurable addon. Add `spec.metricsServer.enabled: true` to the cluster spec to enable.
+  * With this change, one no longer has to set the `--kubelet-insecure-tls` flag, making any `metrics-server` installation **more secure**. See [#6879](https://github.com/kubernetes/kops/issues/6879) for more details.
 
 * Cluster Autoscaler is now availalble as a configurable addon. Add `spec.clusterAutoscaler.enabled: true` to the cluster spec to enable.