mypy: Enable new error explicit-override.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

zilencer/management/commands/compare_messages.py

@@ -2,6 +2,7 @@ from typing import Any
 
 import orjson
 from django.core.management.base import BaseCommand, CommandParser
+from typing_extensions import override
 
 
 class Command(BaseCommand):
@@ -10,10 +11,12 @@ class Command(BaseCommand):
     Usage: ./manage.py compare_messages <dump1> <dump2>
     """
 
+    @override
     def add_arguments(self, parser: CommandParser) -> None:
         parser.add_argument("dump1", help="First file to compare")
         parser.add_argument("dump2", help="Second file to compare")
 
+    @override
     def handle(self, *args: Any, **options: Any) -> None:
         total_count = 0
         changed_count = 0