Fixed typo in docs/ref/migration-operations.txt.

``name`` is the model name, as would be written in the ``models.py`` file.

``fields`` is a list of 2-tuples of ``(field_name, field_instance)``.

The field instance should be an unbound field (so just ``models.CharField()``,

rather than a field takes from another model).

The field instance should be an unbound field (so just

``models.CharField(...)``, rather than a field taken from another model).

``options`` is an optional dictionary of values from the model's ``Meta`` class.