misc: Apply pyupgrade changes for Python 3.12 compatibility

Command applied:
```
find ./backend/ -type f -name "*.py" -exec pyupgrade --py312-plus {} \;
```

backend/handler/database/users_handler.py

@@ -1,4 +1,4 @@
-from typing import Sequence
+from collections.abc import Sequence
 
 from decorators.database import begin_session
 from models.user import Role, User