Merge pull request kubernetes#2615 from wojtek-t/mark_immutable_secrets_done

Mark Immutable secrets/configmaps KEP as implemented

Author: k8s-ci-robot

keps/sig-storage/1412-immutable-secrets-and-configmaps/README.md

@@ -334,6 +334,8 @@ v1.18: Launched in `Alpha`
 
 v1.19: Launched to `Beta`
 
+v1.20: Launched to 'GA'
+
 ## Alternatives
 
 ### Define immutability at VolumeSource level

keps/sig-storage/1412-immutable-secrets-and-configmaps/kep.yaml

@@ -7,7 +7,7 @@ participating-sigs:
   - sig-apps
   - sig-node
   - sig-scalability
-status: implementable
+status: implemented
 reviewers:
   - "@yujuhong"
   - "@lavalamp"