KEP-3619: set implemented in kep.yaml

Author: everpeace

keps/sig-node/3619-supplemental-groups-policy/kep.yaml

@@ -5,7 +5,7 @@ authors:
 owning-sig: sig-node
 participating-sigs:
   - sig-node
-status: implementable
+status: implemented
 creation-date: 2022-10-14
 reviewers:
   - "@thockin"