Replace usage of deprecated translation method

AKSubmission/forms.py

@@ -3,7 +3,7 @@ import re
 
 from django import forms
 from django.core.exceptions import ValidationError
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 
 from AKModel.availability.forms import AvailabilitiesFormMixin
 from AKModel.availability.models import Availability