Revert "Add ignore[arg-type] to fix mypy false positive (#1190)"

This reverts commit 17d0f8e.

It seems that this got resolved by aiohttp version 3.12.14.

Author: agners

matter_server/server/server.py

@@ -89,7 +89,7 @@ async def _handle_shutdown(app: web.Application) -> None:
         for client in set(clients):
             await client.disconnect()
 
-    server.app.on_shutdown.append(_handle_shutdown)  # type: ignore[arg-type]
+    server.app.on_shutdown.append(_handle_shutdown)
     server.app.router.add_route("GET", path, _handle_ws)