Fixed #19024 -- Corrected form wizard docs for get_form_prefix.

    counter as string representing the current step of the wizard. (E.g., the

    first form is ``'0'`` and the second form is ``'1'``)

.. method:: WizardView.get_form_prefix(step)

.. method:: WizardView.get_form_prefix(step, form)

    Given the step, returns a form prefix to use. By default, this simply uses

    the step itself. For more, see the :ref:`form prefix documentation

    <form-prefix>`.

    Given the step and the form class which will be called with the returned

    form prefix. By default, this simply uses the step itself.

    For more, see the :ref:`form prefix documentation <form-prefix>`.

.. method:: WizardView.get_form_initial(step)