release-25.3: Update pkg/testutils/release/cockroach_releases.yaml

Update pkg/testutils/release/cockroach_releases.yaml with recent values.

Epic: None
Release note: None
Release justification: test-only updates

Author: cockroach-teamcity

pkg/testutils/release/cockroach_releases.yaml

@@ -39,5 +39,5 @@
   latest: 25.2.5
   predecessor: "25.1"
 "25.3":
-  latest: 25.3.0
+  latest: 25.3.1
   predecessor: "25.2"