docs(kep): update KEP-3331 status to implemented

Signed-off-by: Anish Ramasekar <anish.ramasekar@gmail.com>

Author: aramase

keps/sig-auth/3331-structured-authentication-configuration/kep.yaml

@@ -10,7 +10,7 @@ reviewers:
 approvers:
 - "@liggitt"
 creation-date: "2022-06-02"
-status: implementable
+status: implemented
 stage: stable
 latest-milestone: "v1.35"
 milestone: