etcd: Update release-etcd team for release window

Add ivanvc to the release-etcd team for release v3.6.0-rc.3.

Author: ivanvc

config/etcd-io/sig-etcd/teams.yaml

@@ -158,7 +158,7 @@ teams:
     description: Granted permission to release etcd-io/etcd
     # The member list is intentionally empty. It should only include the release
     # lead during release windows.
-    members: []
+    members: [ivanvc]
     privacy: closed
     repos:
       etcd: maintain