release-24.3: 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

@@ -41,3 +41,6 @@
 "25.3":
   latest: 25.3.2
   predecessor: "25.2"
+"25.4":
+  latest: 25.4.0-beta.1
+  predecessor: "25.3"