Fixed #13226 -- Corrected typo in authentication docs, thanks rokclimb15.

    :ref:`authentication-backends`) you can pass a custom authentication form

    to the login view via the ``authentication_form`` parameter. This form must

    accept a ``request`` keyword argument in its ``__init__`` method, and

    provide a ``get_user`` argument which returns the authenticated user object

    provide a ``get_user`` method which returns the authenticated user object

    (this method is only ever called after successful form validation).

    .. _forms documentation: ../forms/