ruff: Fix UP035 Import from collections.abc, typing instead.

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

zerver/lib/sessions.py

@@ -1,7 +1,8 @@
 import logging
+from collections.abc import Mapping
 from datetime import timedelta
 from importlib import import_module
-from typing import Any, Mapping, Protocol, cast
+from typing import Any, Protocol, cast
 
 from django.conf import settings
 from django.contrib.auth import SESSION_KEY, get_user_model