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 if _process_task_instances puts a task instance into SKIPPED state if any of its
    upstream tasks are skipped according to TriggerRuleDep.
    """
    clear_db_runs()
    with DAG(
        dag_id='test_task_with_upstream_skip_dag', start_date=DEFAULT_DATE, schedule_interval=None
    ) as dag:
        dummy1 = DummyOperator(task_id='dummy1')
        dummy2 = DummyOperator(task_id="dummy2")
        dummy3 = DummyOperator(task_id="dummy3")
        [dummy1, dummy2] >> dummy3
    
    dag.clear()
    dr = dag.create_dagrun(run_type=DagRunType.MANUAL, state=State.RUNNING, execution_date=DEFAULT_DATE)
    assert dr is not None
    with create_session() as session:
        tis = {ti.task_id: ti for ti in dr.get_task_instances(session=session)}
        
        tis[dummy1.task_id].state = State.SKIPPED
        tis[dummy2.task_id].state = State.SUCCESS
        assert tis[dummy3.task_id].state == State.NONE
    
    
    with create_session() as session:
        tis = {ti.task_id: ti for ti in dr.get_task_instances(session=session)}
        assert tis[dummy1.task_id].state == State.SKIPPED
        assert tis[dummy2.task_id].state == State.SUCCESS
        
        assert tis[dummy3.task_id].state == State.SKIPPED
class TestSchedulerJobQueriesCount(unittest.TestCase):