Fix license field being wrapped in tuple due to trailing comma

Remove trailing comma after license dictionary assignment that was causing the license field to be
stored as a single-element tuple instead of a plain dictionary object.

doi2dataset.py

@@ -1417,7 +1417,7 @@ class MetadataProcessor:
             return_dict["datasetVersion"]["license"] = {
                 "name": license_info.name,
                 "uri": license_info.uri
-            },
+            }
         else:
             return_dict["datasetVersion"]["termsOfUse"] = f"All rights reserved. Copyright © {self._get_publication_year(data)}, [TODO: Insert copyright holder here!]"