### 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
self.scheduler_job.processor_agent = mock.MagicMock()
        
        self.scheduler_job._create_dag_runs([dag_model], session)
        
        assert dag_model.next_dagrun_data_interval_start == DEFAULT_DATE + timedelta(days=1)
        assert dag_model.next_dagrun_data_interval_end == DEFAULT_DATE + timedelta(days=2)
        assert dag_model.next_dagrun == DEFAULT_DATE + timedelta(days=1)
        session.rollback()
    @conf_vars({('scheduler', 'use_job_schedule'): "false"})
    def test_do_schedule_max_active_runs_dag_timed_out(self, dag_maker):
        """Test that tasks are set to a finished state when their DAG times out"""
        with dag_maker(
            dag_id='test_max_active_run_with_dag_timed_out',
            schedule_interval='@once',
            max_active_runs=1,
            catchup=True,
            dagrun_timeout=datetime.timedelta(seconds=1),
        ) as dag:
            task1 = BashOperator(
                task_id='task1',
                bash_command=' for((i=1;i<=600;i+=1)); do sleep "$i";  done',
            )
        session = settings.Session()
        run1 = dag.create_dagrun(
            run_type=DagRunType.SCHEDULED,
            execution_date=DEFAULT_DATE,
            state=State.RUNNING,
            start_date=timezone.utcnow() - timedelta(seconds=2),
            session=session,
        )