Update milestone to 1.27

Author: xing-yang

keps/sig-storage/3476-volume-group/kep.yaml

@@ -18,12 +18,12 @@ approvers:
 see-also:
 replaces:
 
-latest-milestone: "v1.26"
+latest-milestone: "v1.27"
 stage: "alpha"
 milestone:
-  alpha: "v1.26"
-  beta: "v1.27"
-  stable: "v1.28"
+  alpha: "v1.27"
+  beta: "v1.29"
+  stable: "v1.31"
 
 feature-gates:
 disable-supported: true