Update traitsdoc.py

The update fixes the following:

Exception occurred:
  File "d:\pyenvs\cti-soap\lib\site-packages\numpydoc\numpydoc.py", line 36, in mangle_docstrings
    doc = get_doc_object(obj, what, u"\n".join(lines), config=cfg)
TypeError: get_doc_object() got multiple values for keyword argument 'config'