Corrected headings in migration docs.

AlterOrderWithRespectTo

-----------------------

.. class:: AlterIndexTogether(name, order_with_respect_to)

.. class:: AlterOrderWithRespectTo(name, order_with_respect_to)

Makes or deletes the ``_order`` column needed for the

:attr:`~django.db.models.Options.order_with_respect_to` option on the ``Meta``

AlterModelOptions

-----------------

.. class:: AlterIndexTogether(name, options)

.. class:: AlterModelOptions(name, options)

Stores changes to miscellaneous model options (settings on a model's ``Meta``)

like ``permissions`` and ``verbose_name``. Does not affect the database, but

persists these changes for :class:`RunPython` instances to use.

persists these changes for :class:`RunPython` instances to use. ``options``

should be a dictionary mapping option names to values.

AddField

--------