### Body

Add unit test for changes in https://github.com/apache/airflow/pull/17305

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.
tests/jobs/test_backfill_job.py
"""
        Test that queued tasks are executed by BackfillJob
        """
        session = settings.Session()
        pool = Pool(pool='test_backfill_pooled_task_pool', slots=1)
        session.add(pool)
        session.commit()
        session.close()
        dag = self.dagbag.get_dag('test_backfill_pooled_task_dag')
        dag.clear()
        executor = MockExecutor(do_update=True)
        job = BackfillJob(dag=dag, start_date=DEFAULT_DATE, end_date=DEFAULT_DATE, executor=executor)
        
        
        try:
            with timeout(seconds=5):
                job.run()
        except AirflowTaskTimeout:
            pass
        ti = TI(task=dag.get_task('test_backfill_pooled_task'), execution_date=DEFAULT_DATE)
        ti.refresh_from_db()
        assert ti.state == State.SUCCESS
    @pytest.mark.quarantined
    def test_backfill_depends_on_past(self):