This tests fails occasionally on mysql at least:

https://github.com/apache/airflow/pull/11555/checks?check_run_id=1260840314#step:9:1125

```
=================================== FAILURES ===================================
_____________ TestSchedulerJob.test_no_orphan_process_will_be_left _____________

self = <tests.jobs.test_scheduler_job.TestSchedulerJob testMethod=test_no_orphan_process_will_be_left>

    def test_no_orphan_process_will_be_left(self):
        empty_dir = mkdtemp()
        current_process = psutil.Process()
        old_children = current_process.children(recursive=True)
        scheduler = SchedulerJob(subdir=empty_dir,
                                 num_runs=1,
                                 executor=MockExecutor(do_update=False))
        scheduler.run()
        shutil.rmtree(empty_dir)
    
        # Remove potential noise created by previous tests.
        current_children = set(current_process.children(recursive=True)) - set(
            old_children)
>       self.assertFalse(current_children)
E       AssertionError: {psutil.Process(pid=3474, name='/usr/local/bin/', status='running', started='19:26:22')} is not false

tests/jobs/test_scheduler_job.py:871: AssertionError
```



tests/jobs/test_scheduler_job.py
dag_id = 'test_adopt_or_reset_orphaned_tasks_stale_scheduler_jobs'
        dag = DAG(dag_id=dag_id, start_date=DEFAULT_DATE, schedule_interval='@daily')
        DummyOperator(task_id='task1', dag=dag)
        DummyOperator(task_id='task2', dag=dag)
        scheduler_job = SchedulerJob(subdir=os.devnull)
        session = settings.Session()
        scheduler_job.state = State.RUNNING
        scheduler_job.latest_heartbeat = timezone.utcnow()
        session.add(scheduler_job)
        old_job = SchedulerJob(subdir=os.devnull)
        old_job.state = State.RUNNING
        old_job.latest_heartbeat = timezone.utcnow() - timedelta(minutes=15)
        session.add(old_job)
        session.flush()
        dr1 = dag.create_dagrun(
            run_type=DagRunType.SCHEDULED,
            execution_date=DEFAULT_DATE,
            start_date=timezone.utcnow(),
            state=State.RUNNING,
            session=session,