Fix concurrency note for stream_object_data

Author: EliahKagan

Diff for: git/cmd.py

@@ -1572,8 +1572,8 @@ def stream_object_data(self, ref: str) -> Tuple[str, str, int, "Git.CatFileConte
             (hexsha, type_string, size_as_int, stream)
 
         :note:
-            This method is not threadsafe. You need one independent Command instance per
-            thread to be safe!
+            This method is not threadsafe. You need one independent :class:`Git`
+            instance per thread to be safe!
         """
         cmd = self._get_persistent_cmd("cat_file_all", "cat_file", batch=True)
         hexsha, typename, size = self.__get_object_header(cmd, ref)