KEP-3857: Recursive Read-only (RRO) mounts: mark as implemented

The feature has been already implemented.
(Alpha: v1.30, Beta: v1.31, GA: v1.33)

Signed-off-by: Akihiro Suda <[email protected]>

Author: AkihiroSuda

keps/sig-node/3857-rro-mounts/kep.yaml

@@ -6,7 +6,7 @@ owning-sig: sig-node
 #participating-sigs:
 #  - sig-aaa
 #  - sig-bbb
-status: implementable
+status: implemented
 creation-date: 2023-02-09
 reviewers:
   - "@thockin"