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
"""
        Test that ignore_first_depends_on_past doesn't affect results
        (this is the same test as
        test_dagrun_deadlock_ignore_depends_on_past_advance_ex_date except
        that start_date == execution_date so depends_on_past is irrelevant).
        """
        self.evaluate_dagrun(
            dag_id='test_dagrun_states_deadlock',
            expected_task_states={
                'test_depends_on_past': State.SUCCESS,
                'test_depends_on_past_2': State.SUCCESS,
            },
            dagrun_state=State.SUCCESS,
            run_kwargs=dict(ignore_first_depends_on_past=True),
        )
    def test_scheduler_start_date(self):
        """
        Test that the scheduler respects start_dates, even when DAGS have run
        """
        with create_session() as session:
            dag_id = 'test_start_date_scheduling'
            dag = self.dagbag.get_dag(dag_id)
            dag.clear()
            assert dag.start_date > datetime.datetime.now(timezone.utc)