Refs #26142 -- Documented that Formset's extra=0 doesn't prevent creating objects.

    >>> [x.name for x in formset.get_queryset()]

    ['Charles Baudelaire', 'Paul Verlaine', 'Walt Whitman']

Also, ``extra=0`` doesn't prevent creation of new model instances as you can

:ref:`add additional forms with JavaScript <understanding-the-managementform>`

or just send additional POST data. Formsets `don't yet provide functionality

<https://code.djangoproject.com/ticket/26142>`_ for an "edit only" view that

prevents creation of new instances.

If the value of ``max_num`` is greater than the number of existing related

objects, up to ``extra`` additional blank forms will be added to the formset,

so long as the total number of forms does not exceed ``max_num``::