Fix test_published_date_is_not_changed_when_publishing_twice.
Fix test_published_date_is_not_changed_when_publishing_twice.

jp74/django-model-publisher,jp74/django-model-publisher,wearehoods/django-model-publisher-ai,jp74/django-model-publisher,wearehoods/django-model-publisher-ai,wearehoods/django-model-publisher-ai