Adding missing comma to Protobuf maintainers metadata

PiperOrigin-RevId: 847825454

Author: karenwuz

.bcr/metadata.template.json

@@ -104,7 +104,7 @@
       "github": "pilgrimmemoirs",
       "name": "Jamie Pilgrim",
       "do_not_notify": true
-    }
+    },
     {
       "email": "[email protected]",
       "github": "karenwuz",