### 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
dag_id = 'test_backfill_max_limit_check'
        run_id = 'test_dag_run'
        start_date = DEFAULT_DATE - datetime.timedelta(hours=1)
        end_date = DEFAULT_DATE
        dag_run_created_cond = threading.Condition()
        def run_backfill(cond):
            cond.acquire()
            
            with create_session() as thread_session:
                try:
                    dag = self._get_dag_test_max_active_limits(
                        dag_maker,
                        dag_id=dag_id,
                    )
                    dag_maker.create_dagrun(
                        
                        run_id=run_id,
                        execution_date=DEFAULT_DATE + datetime.timedelta(hours=1),
                    )
                    thread_session.commit()
                    cond.notify()
                finally:
                    cond.release()
                    thread_session.close()
                executor = MockExecutor()
                job = BackfillJob(