Fix another flake8 warning.

I don't agree with flake8 here about the right indentation, but as long as
we're using it, we should stick to it. I don't want to disable its hanging
indent checks just because of this case.

django/views/generic/dates.py

@@ -654,8 +654,8 @@ class BaseDateDetailView(YearMixin, MonthMixin, DayMixin, DateMixin, BaseDetailV
             raise Http404(_(
                 "Future %(verbose_name_plural)s not available because "
                 "%(class_name)s.allow_future is False.") % {
-                    'verbose_name_plural': qs.model._meta.verbose_name_plural,
-                    'class_name': self.__class__.__name__,
+                'verbose_name_plural': qs.model._meta.verbose_name_plural,
+                'class_name': self.__class__.__name__,
                 },
             )