### 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
)
        sdag.clear(start_date=DEFAULT_DATE, end_date=DEFAULT_DATE, include_parentdag=True)
        ti_subdag.refresh_from_db()
        assert State.NONE == ti_subdag.state
        ti_irrelevant.refresh_from_db()
        assert State.SUCCESS == ti_irrelevant.state
        ti_downstream.refresh_from_db()
        assert State.NONE == ti_downstream.state
        subdag.clear()
        dag.clear()
    def test_backfill_execute_subdag_with_removed_task(self):
        """
        Ensure that subdag operators execute properly in the case where
        an associated task of the subdag has been removed from the dag
        definition, but has instances in the database from previous runs.
        """
        dag = self.dagbag.get_dag('example_subdag_operator')
        subdag = dag.get_task('section-1').subdag
        session = settings.Session()
        executor = MockExecutor()
        job = BackfillJob(
            dag=subdag, start_date=DEFAULT_DATE, end_date=DEFAULT_DATE, executor=executor, donot_pickle=True
        )
        dr = DagRun(
            dag_id=subdag.dag_id, execution_date=DEFAULT_DATE, run_id="test", run_type=DagRunType.BACKFILL_JOB
        )
        session.add(dr)
        removed_task_ti = TI(
            task=DummyOperator(task_id='removed_task'), run_id=dr.run_id, state=State.REMOVED
        )