Fixed typo in docs/model-api.txt

        list_display = ('username', 'email', 'first_name', 'last_name', 'is_staff'),

        list_filter = ('is_staff', 'is_superuser'),

    This results in a admin that looks like:

    The above code results in an admin that looks like this:

        .. image:: http://media.djangoproject.com/img/doc/users_changelist.png