### 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 = "test_process_executor_events"
        task_id_1 = 'dummy_task'
        session = settings.Session()
        with dag_maker(dag_id=dag_id, fileloc='/test_path1/'):
            task1 = DummyOperator(task_id=task_id_1)
        ti1 = dag_maker.create_dagrun().get_task_instance(task1.task_id)
        mock_stats_incr.reset_mock()
        executor = MockExecutor(do_update=False)
        task_callback = mock.MagicMock()
        mock_task_callback.return_value = task_callback
        self.scheduler_job = SchedulerJob(executor=executor)
        self.scheduler_job.processor_agent = mock.MagicMock()
        ti1.state = State.QUEUED
        session.merge(ti1)
        session.commit()
        executor.event_buffer[ti1.key] = State.FAILED, None
        self.scheduler_job._process_executor_events(session=session)
        ti1.refresh_from_db(session=session)
        assert ti1.state == State.FAILED
        self.scheduler_job.processor_agent.send_callback_to_execute.assert_not_called()
        self.scheduler_job.processor_agent.reset_mock()
        
        ti1.state = State.SUCCESS
        session.merge(ti1)
        session.commit()
        executor.event_buffer[ti1.key] = State.SUCCESS, None
        self.scheduler_job._process_executor_events(session=session)