### 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
@pytest.mark.parametrize("state, msg", [[State.SUCCESS, 'success'], [State.FAILED, 'task_failure']])
    def test_dagrun_callbacks_are_added_when_callbacks_are_defined(self, state, msg, dag_maker):
        """
        Test if on_*_callback are defined on DAG, Callbacks ARE registered and sent to DAG Processor
        """
        with dag_maker(
            dag_id='test_dagrun_callbacks_are_added_when_callbacks_are_defined',
            on_failure_callback=lambda: True,
            on_success_callback=lambda: True,
        ):
            BashOperator(task_id='test_task', bash_command='echo hi')
        self.scheduler_job = SchedulerJob(subdir=os.devnull)
        self.scheduler_job.processor_agent = mock.Mock()
        self.scheduler_job.processor_agent.send_callback_to_execute = mock.Mock()
        self.scheduler_job._send_dag_callbacks_to_processor = mock.Mock()
        session = settings.Session()
        dr = dag_maker.create_dagrun()
        ti = dr.get_task_instance('test_task')
        ti.set_state(state, session)
        with mock.patch.object(settings, "USE_JOB_SCHEDULE", False):
            self.scheduler_job._do_scheduling(session)
        
        self.scheduler_job._send_dag_callbacks_to_processor.assert_called_once()
        call_args = self.scheduler_job._send_dag_callbacks_to_processor.call_args[0]
        assert call_args[0].dag_id == dr.dag_id
        assert call_args[1] is not None
        assert call_args[1].msg == msg
        session.rollback()
        session.close()
    def test_do_not_schedule_removed_task(self, dag_maker):