2to3: Skip `funcattrs` fixer.

In Python 3 the func.func_name attribute is replaced by the
func.__name__ attribute. The only file affected by this is
doc/sphinxext/numpydoc/phantom_import.py, and there its use
is already version dependent.

Closes #3054.
Merge pull request #3227 from charris/2to3-apply-funcattrs

2to3: Skip `funcattrs` fixer.