Fixed incorrect pluralized argument in Files docs

    to point to it. If ``save`` is ``True``, the model's ``save()`` method will

    be called once the file is saved. That is, these two lines::

        >>> car.photo.save('myphoto.jpg', contents, save=False)

        >>> car.photo.save('myphoto.jpg', content, save=False)

        >>> car.save()

    are the same as this one line::

        >>> car.photo.save('myphoto.jpg', contents, save=True)

        >>> car.photo.save('myphoto.jpg', content, save=True)

    Note that the ``content`` argument must be an instance of either

    :class:`File` or of a subclass of :class:`File`, such as