### 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
dag_id = 'SchedulerJobTest.test_find_executable_task_instances_max_active_tis_per_dag'
        task_id_1 = 'dummy'
        task_id_2 = 'dummy2'
        with dag_maker(dag_id=dag_id, max_active_tasks=16):
            task1 = DummyOperator(task_id=task_id_1, max_active_tis_per_dag=2)
            task2 = DummyOperator(task_id=task_id_2)
        executor = MockExecutor(do_update=True)
        self.scheduler_job = SchedulerJob(executor=executor)
        session = settings.Session()
        dr1 = dag_maker.create_dagrun(run_type=DagRunType.SCHEDULED)
        dr2 = dag_maker.create_dagrun_after(dr1, run_type=DagRunType.SCHEDULED)
        dr3 = dag_maker.create_dagrun_after(dr2, run_type=DagRunType.SCHEDULED)
        ti1_1 = dr1.get_task_instance(task1.task_id)
        ti2 = dr1.get_task_instance(task2.task_id)
        ti1_1.state = State.SCHEDULED
        ti2.state = State.SCHEDULED
        session.merge(ti1_1)
        session.merge(ti2)
        session.flush()
        res = self.scheduler_job._executable_task_instances_to_queued(max_tis=32, session=session)
        assert 2 == len(res)
        ti1_1.state = State.RUNNING
        ti2.state = State.RUNNING
        ti1_2 = dr2.get_task_instance(task1.task_id)
        ti1_2.state = State.SCHEDULED
        session.merge(ti1_1)
        session.merge(ti2)
        session.merge(ti1_2)
        session.flush()