Fixed #23343 -- Typo in docs/ref/class-based-views/generic-date-based.txt.

      month or day using the attribute ``date_list_period``. This also applies

      to all subclass views.

    **Example myapp/views.py**::

    **Example myapp/urls.py**::

        from django.conf.urls import url

        from django.views.generic.dates import ArchiveIndexView