Use Python-3-style super calls

Created by: das-g

IIRC, we've dropped Python 2.7 compatibility for OSMaxx early on. Despite that, we still have some Python-2-style super calls:

$> git grep 'super([^)]' -- '*.py'
osmaxx/contrib/auth/frontend_permissions.py:        return super(LoginRequiredMixin, self).dispatch(*args, **kwargs)
osmaxx/contrib/auth/frontend_permissions.py:        return super(FrontendAccessRequiredMixin, self).dispatch(*args, **kwargs)
osmaxx/excerptexport/forms/excerpt_form.py:        super(ExcerptForm, self).__init__(*args, **kwargs)
osmaxx/excerptexport/forms/existing_form.py:        super(ExistingForm, self).__init__(*args, **kwargs)
osmaxx/excerptexport/views.py:        return super(DeleteExcerptView, self).delete(request, *args, **kwargs)
tests/excerptexport/models/test_export_model.py:        super(TimeStampModelMixin, self).save(*args, **kwargs)
tests/utilities/test_models/models.py:        return super(ArticleManager, self).get_queryset().filter(authors__name__icontains='sir')

We should replace them by Python-3-style super calls (i.e. without any arguments).