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_registration/views.py

@@ -6,7 +6,7 @@ from django.contrib import messages
 from django.db.models import Q
 from django.http import JsonResponse
 from django.urls import reverse_lazy
-from django.utils.translation import ugettext as _
+from django.utils.translation import gettext as _
 from django.views import generic
 
 from dav_events.choices import SPORT_CHOICES, LEVEL_CHOICES