update object storage (kubernetes#1979) alpha milestone to v1.25

Author: wlan0

keps/sig-storage/1979-object-storage-support/kep.yaml

@@ -22,6 +22,6 @@ creation-date: 2019-11-25
 last-updated: 2022-04-06
 status: alpha
 stage: alpha
-latest-milestone: v1.24
+latest-milestone: v1.25
 milestone:
-  alpha: "v1.24"
+  alpha: "v1.25"