Update ref-statuses.json to new valid Git refs list

Author: lucperkins

ref-statuses.json

@@ -3,6 +3,8 @@
   "nixos-24.05-small": "unmaintained",
   "nixos-24.11": "stable",
   "nixos-24.11-small": "stable",
+  "nixos-25.05": "beta",
+  "nixos-25.05-small": "beta",
   "nixos-unstable": "rolling",
   "nixos-unstable-small": "rolling",
   "nixpkgs-24.05-darwin": "unmaintained",