Use 3.12.0 final for the seconday umbrella

Author: HoloRin

bazel/bzlmod/secondary_umbrella.bzl

@@ -28,9 +28,9 @@ def secondary_umbrella():
         name = "rabbitmq-server-generic-unix-3.12",
         build_file = "@//:BUILD.package_generic_unix",
         patch_cmds = [ADD_PLUGINS_DIR_BUILD_FILE],
-        strip_prefix = "rabbitmq_server-3.12.0-rc.3",
+        strip_prefix = "rabbitmq_server-3.12.0",
         # This file is produced just in time by the test-mixed-versions.yaml GitHub Actions workflow.
         urls = [
-            "https://rabbitmq-github-actions.s3.eu-west-1.amazonaws.com/secondary-umbrellas/package-generic-unix-for-mixed-version-testing-v3.12.0-rc.3.tar.xz",
+            "https://rabbitmq-github-actions.s3.eu-west-1.amazonaws.com/secondary-umbrellas/package-generic-unix-for-mixed-version-testing-v3.12.0.tar.xz",
         ],
     )