Replaced ugettext and ugettext_lazy with gettext and gettext_lazy

ugettext and ugettext_lazy were deprecated in Django 3 and will be
removed in Django 4.

dav_events/workflow.py

@@ -5,7 +5,7 @@ import re
 from django.apps import apps
 from django.db.models.functions import Length
 from django.utils import timezone
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 
 from . import emails
 from . import signals