### Body

The `test_no_orphan_process_will_be_left` in `TestSchedulerJob` is really flaky.

Before we know how to fix it, I will quarantine it:

https://github.com/apache/airflow/pull/18691/checks?check_run_id=3811660138

```
  =================================== FAILURES ===================================
  _____________ TestSchedulerJob.test_no_orphan_process_will_be_left _____________
  
  self = <tests.jobs.test_scheduler_job.TestSchedulerJob object at 0x7fc2f91d2ac8>
  
      def test_no_orphan_process_will_be_left(self):
          empty_dir = mkdtemp()
          current_process = psutil.Process()
          old_children = current_process.children(recursive=True)
          self.scheduler_job = SchedulerJob(
              subdir=empty_dir, num_runs=1, executor=MockExecutor(do_update=False)
          )
          self.scheduler_job.run()
          shutil.rmtree(empty_dir)
      
          # Remove potential noise created by previous tests.
          current_children = set(current_process.children(recursive=True)) - set(old_children)
  >       assert not current_children
  E       AssertionError: assert not {psutil.Process(pid=2895, name='pytest', status='running', started='06:53:45')}
  
```

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.
tests/jobs/test_scheduler_job.py
"""
        Test that dagrun timeout fails run and update the next dagrun
        """
        session = settings.Session()
        with dag_maker(
            max_active_runs=1,
            dag_id='test_scheduler_fail_dagrun_timeout',
            dagrun_timeout=datetime.timedelta(seconds=60),
        ):
            DummyOperator(task_id='dummy')
        dr = dag_maker.create_dagrun(start_date=timezone.utcnow() - datetime.timedelta(days=1))
        
        dag_maker.dag_model.next_dagrun == dr.execution_date
        self.scheduler_job = SchedulerJob(subdir=os.devnull)
        self.scheduler_job.dagbag = dag_maker.dagbag
        
        self.scheduler_job.processor_agent = mock.Mock()
        self.scheduler_job.processor_agent.send_callback_to_execute = mock.Mock()
        self.scheduler_job._schedule_dag_run(dr, session)
        session.flush()
        session.refresh(dr)
        assert dr.state == State.FAILED
        
        assert dag_maker.dag_model.next_dagrun_create_after == dr.execution_date + timedelta(days=1)
        
        assert (
            session.query(DagRun).filter(DagRun.state.in_([DagRunState.RUNNING, DagRunState.QUEUED])).count()
            == 0
        )
    @pytest.mark.parametrize(