fix subscription

enrollments-events/app/enrollment.py

@@ -2,7 +2,7 @@ from abc import ABC
 from dataclasses import dataclass
 from datetime import timedelta
 from enum import Enum
-from typing import NotRequired, TypedDict
+from typing import TypedDict
 
 from layercake.dateutils import now, ttl
 from layercake.dynamodb import DynamoDBPersistenceLayer
@@ -31,7 +31,7 @@ Subscription = TypedDict(
     {
         'org_id': str,
         'billing_day': int,
-        'billing_period': NotRequired[str],
+        'billing_period': str,
     },
 )