### 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
"""
        DagRuns with one unfinished and one failed root task -> RUNNING
        """
        
        
        dag_id = 'test_dagrun_states_root_fail_unfinished'
        dag = self.dagbag.get_dag(dag_id)
        dr = dag.create_dagrun(
            run_type=DagRunType.SCHEDULED,
            execution_date=DEFAULT_DATE,
            state=State.RUNNING,
        )
        self.null_exec.mock_task_fail(dag_id, 'test_dagrun_fail', dr.run_id)
        with pytest.raises(AirflowException):
            dag.run(start_date=dr.execution_date, end_date=dr.execution_date, executor=self.null_exec)
        
        
        with create_session() as session:
            ti = dr.get_task_instance('test_dagrun_unfinished', session=session)
            ti.state = State.NONE
            session.commit()
        dr.update_state()
        assert dr.state == State.RUNNING
    def test_dagrun_root_after_dagrun_unfinished(self):