### 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 SLA Callbacks are not sent when no task SLAs are defined"""
        dag_id = 'test_send_sla_callbacks_to_processor_sla_no_task_slas'
        with dag_maker(dag_id=dag_id, schedule_interval='@daily') as dag:
            DummyOperator(task_id='task1')
        with patch.object(settings, "CHECK_SLAS", True):
            self.scheduler_job = SchedulerJob(subdir=os.devnull)
            mock_agent = mock.MagicMock()
            self.scheduler_job.processor_agent = mock_agent
            self.scheduler_job._send_sla_callbacks_to_processor(dag)
            self.scheduler_job.processor_agent.send_sla_callback_request_to_execute.assert_not_called()
    def test_send_sla_callbacks_to_processor_sla_with_task_slas(self, dag_maker):
        """Test SLA Callbacks are sent to the DAG Processor when SLAs are defined on tasks"""
        dag_id = 'test_send_sla_callbacks_to_processor_sla_with_task_slas'
        with dag_maker(dag_id=dag_id, schedule_interval='@daily') as dag:
            DummyOperator(task_id='task1', sla=timedelta(seconds=60))
        with patch.object(settings, "CHECK_SLAS", True):
            self.scheduler_job = SchedulerJob(subdir=os.devnull)
            mock_agent = mock.MagicMock()
            self.scheduler_job.processor_agent = mock_agent
            self.scheduler_job._send_sla_callbacks_to_processor(dag)
            self.scheduler_job.processor_agent.send_sla_callback_request_to_execute.assert_called_once_with(
                full_filepath=dag.fileloc, dag_id=dag_id
            )
    def test_create_dag_runs(self, dag_maker):