feat(api): replace pytz with zoneinfo

Part-of: <https://dev.funkwhale.audio/funkwhale/funkwhale/-/merge_requests/2388>

api/funkwhale_api/users/factories.py

@@ -1,5 +1,6 @@
+import sys
+
 import factory
-import pytz
 from django.contrib.auth.models import Permission
 from django.utils import timezone
 
@@ -7,6 +8,11 @@ from funkwhale_api.factories import ManyToManyFromList, NoUpdateOnCreate, regist
 
 from . import models
 
+if sys.version_info < (3, 9):
+    from backports.zoneinfo import ZoneInfo
+else:
+    from zoneinfo import ZoneInfo
+
 
 @registry.register
 class GroupFactory(NoUpdateOnCreate, factory.django.DjangoModelFactory):
@@ -159,7 +165,7 @@ class GrantFactory(factory.django.DjangoModelFactory):
 class AccessTokenFactory(factory.django.DjangoModelFactory):
     application = factory.SubFactory(ApplicationFactory)
     user = factory.SubFactory(UserFactory)
-    expires = factory.Faker("future_datetime", tzinfo=pytz.UTC)
+    expires = factory.Faker("future_datetime", tzinfo=ZoneInfo("UTC"))
     token = factory.Faker("uuid4")
     scope = "read"