utilities/autowrap: Remove :ref: tag from docstring

The :ref: tag was used in some Sphinx docs. At some point in the past,
the documentation was moved directly to the .py file, where it is
(apparently) impossible to use the :ref: tag. Remove it and instead just
emphasize the function name. This fixes an error thrown by Sphinx.

sympy/utilities/autowrap.py

@@ -49,7 +49,7 @@
        binaries immediately from within SymPy.
 
     4) To create customized ufuncs for use with numpy arrays.
-       See :ref:`ufuncify`
+       See *ufuncify*.
 
 When is this module NOT the best approach?