Increase test timeout when quitting pending jobs

```
        yield
        # qapp.backup_cancelled_event.emit()
>       qtbot.waitUntil(lambda: not vorta.borg.job_scheduler.JobsManager.is_worker_running())
E       pytestqt.exceptions.TimeoutError: waitUntil timed out in 5000 milliseconds

tests/conftest.py:76: TimeoutError
```