add prr reviewer

Author: Han Kang

keps/prod-readiness/sig-instrumentation/3498.yaml

@@ -4,3 +4,5 @@
 kep-number: 3498
 alpha:
   approver: "@wojtek-t"
+beta:
+  approver: "@wojtek-t"

keps/sig-instrumentation/3498-extending-stability/README.md

@@ -347,7 +347,7 @@ No.
 
 ###### How can an operator determine if the feature is in use by workloads?
 
-Dependence on any Kubernetes control-plane metrics implies that they are using this feature.
+We've introduced a metric (i.e. `registered_metrics_total`) which should serve to indicate this feature is enabled.
 
 ###### How can someone using this feature know that it is working for their instance?