fix: missing comma

Author: samrose

nix/ext/versions.json

@@ -462,7 +462,7 @@
       ],
       "hash": "sha256-vR3MvfmUP2QEAtXFpq0NCCKck3wZPD+H3QleHtyVQJs=",
       "revision": "2.7.11"
-    }
+    },
     "2.8.11": {
       "postgresql": [
         "15",