Fix type error in 2.7 stubs (#152)

stdlib/2.7/argparse.pyi

@@ -135,7 +135,7 @@ class _ActionsContainer:
         help: str = ...,
         metavar: str = ...,
         dest: str = ...,
-        version: str = ...,
+        version: str = ...
     ) -> None: ...
     def add_argument_group(self, *args, **kwargs): ...
     def add_mutually_exclusive_group(self, **kwargs): ...