add some documentation around the metrics stability migration changes for clarity

pkg/ssh/ssh.go

@@ -46,6 +46,14 @@ import (
 	"k8s.io/klog"
 )
 
+/*
+ * By default, all the following metrics are defined as falling under
+ * ALPHA stability level https://github.com/kubernetes/enhancements/blob/master/keps/sig-instrumentation/20190404-kubernetes-control-plane-metrics-stability.md#stability-classes)
+ *
+ * Promoting the stability level of the metric is a responsibility of the component owner, since it
+ * involves explicitly acknowledging support for the metric across multiple releases, in accordance with
+ * the metric stability policy.
+ */
 var (
 	tunnelOpenCounter = metrics.NewCounter(
 		&metrics.CounterOpts{