update the state of KEP CSIServiceAccountToken

Author: zshihang

keps/sig-storage/1855-csi-driver-service-account-token/kep.yaml

@@ -15,8 +15,8 @@ approvers:
   - "@msau42"
   - "@mikedanese"
 creation-date: 2020-06-09
-last-updated: 2021-04-29
-status: implementable
+last-updated: 2021-08-19
+status: implemented
 stage: stable
 latest-milestone: "v1.22"
 milestone: