ref: replace handmade UTC_0 with datetime.UTC (#65258)

<!-- Describe your PR here. -->

src/sentry/backup/helpers.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from datetime import datetime, timedelta, timezone
+from datetime import UTC, datetime
 from enum import Enum
 from typing import Generic, NamedTuple, TypeVar
 
@@ -10,8 +10,6 @@ from django.db import models
 # Django apps we take care to never import or export from.
 EXCLUDED_APPS = frozenset(("auth", "contenttypes", "fixtures"))
 
-UTC_0 = timezone(timedelta(hours=0))
-
 
 class Printer:
     """
@@ -47,7 +45,7 @@ class DatetimeSafeDjangoJSONEncoder(DjangoJSONEncoder):
 
     def default(self, obj):
         if isinstance(obj, datetime):
-            return obj.astimezone(UTC_0).strftime("%Y-%m-%dT%H:%M:%S.%f")[:-3] + "Z"
+            return obj.astimezone(UTC).strftime("%Y-%m-%dT%H:%M:%S.%f")[:-3] + "Z"
         return super().default(obj)