### 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 that task instances follow execution_date order priority. If two dagruns with
        different execution dates are scheduled, tasks with earliest dagrun execution date will first
        be executed
        """
        dag_id_1 = 'SchedulerJobTest.test_find_executable_task_instances_order_execution_date-a'
        dag_id_2 = 'SchedulerJobTest.test_find_executable_task_instances_order_execution_date-b'
        task_id = 'task-a'
        session = settings.Session()
        with dag_maker(dag_id=dag_id_1, max_active_tasks=16, session=session):
            DummyOperator(task_id=task_id)
        dr1 = dag_maker.create_dagrun(execution_date=DEFAULT_DATE + timedelta(hours=1))
        with dag_maker(dag_id=dag_id_2, max_active_tasks=16, session=session):
            DummyOperator(task_id=task_id)
        dr2 = dag_maker.create_dagrun()
        dr1 = session.merge(dr1, load=False)
        self.scheduler_job = SchedulerJob(subdir=os.devnull)
        tis = dr1.task_instances + dr2.task_instances
        for ti in tis:
            ti.state = State.SCHEDULED
            session.merge(ti)
        session.flush()
        res = self.scheduler_job._executable_task_instances_to_queued(max_tis=1, session=session)
        session.flush()
        assert [ti.key for ti in res] == [tis[1].key]
        session.rollback()
    def test_find_executable_task_instances_order_priority(self, dag_maker):