reference: remove duplicate py3c_PyFile_AsFileWithMode definition
reference: remove duplicate py3c_PyFile_AsFileWithMode definition

The following warning is emitted by sphinx:

    reference.rst:646:
    WARNING: duplicate C object description of py3c_PyFile_AsFileWithMode,
    other instance in fileshim.rst

Remove the duplicate definition.

Signed-off-by: David Aguilar <9de348c050f7cd1ca590883733c4e531ce610bf4@gmail.com>

encukou/py3c,encukou/py3c,encukou/py3c