### 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.heartbeat = mock.MagicMock()
            self.scheduler_job.processor_agent = mock_agent
            failures = []  
            message = "Expected {expected_count} query, but got {current_count} located at:"
            for expected_query_count in expected_query_counts:
                with create_session() as session:
                    try:
                        with assert_queries_count(expected_query_count, message):
                            self.scheduler_job._do_scheduling(session)
                    except AssertionError as e:
                        failures.append(str(e))
            if failures:
                prefix = "Collected database query count mismatches:"
                joined = "\n\n".join(failures)
                raise AssertionError(f"{prefix}\n\n{joined}")
    def test_should_mark_dummy_task_as_success(self):
        dag_file = os.path.join(
            os.path.dirname(os.path.realpath(__file__)), '../dags/test_only_dummy_tasks.py'
        )
        
        dagbag = DagBag(dag_folder=dag_file, include_examples=False, read_dags_from_db=False)
        dagbag.sync_to_db()
        self.scheduler_job = SchedulerJob(subdir=os.devnull)
        self.scheduler_job.processor_agent = mock.MagicMock()
        dag = self.scheduler_job.dagbag.get_dag("test_only_dummy_tasks")
        
        session = settings.Session()
        orm_dag = session.query(DagModel).get(dag.dag_id)
        self.scheduler_job._create_dag_runs([orm_dag], session)
        drs = DagRun.find(dag_id=dag.dag_id, session=session)