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
([20, 11, 11, 11], 1, 1, "1d", "@once", "linear"),  
            ([20, 21, 23, 25], 1, 1, "1d", "30m", "no_structure"),  
            ([20, 21, 23, 25], 1, 1, "1d", "30m", "linear"),  
            ([20, 21, 23, 25], 1, 1, "1d", "30m", "binary_tree"),  
            ([20, 21, 23, 25], 1, 1, "1d", "30m", "star"),  
            ([20, 21, 23, 25], 1, 1, "1d", "30m", "grid"),  
            
            ([8, 8, 8, 8], 1, 5, "1d", "None", "no_structure"),  
            ([8, 8, 8, 8], 1, 5, "1d", "None", "linear"),  
            ([20, 11, 11, 11], 1, 5, "1d", "@once", "no_structure"),  
            ([21, 12, 12, 12], 1, 5, "1d", "@once", "linear"),  
            ([20, 21, 23, 25], 1, 5, "1d", "30m", "no_structure"),  
            ([21, 23, 26, 29], 1, 5, "1d", "30m", "linear"),  
            ([21, 23, 26, 29], 1, 5, "1d", "30m", "binary_tree"),  
            ([21, 23, 26, 29], 1, 5, "1d", "30m", "star"),  
            ([21, 23, 26, 29], 1, 5, "1d", "30m", "grid"),  
            
            ([8, 8, 8, 8], 10, 10, "1d", "None", "no_structure"),  
            ([8, 8, 8, 8], 10, 10, "1d", "None", "linear"),  
            ([83, 26, 26, 26], 10, 10, "1d", "@once", "no_structure"),  
            ([93, 39, 39, 39], 10, 10, "1d", "@once", "linear"),  
            ([83, 87, 87, 87], 10, 10, "1d", "30m", "no_structure"),  
            ([93, 113, 113, 113], 10, 10, "1d", "30m", "linear"),  
            ([93, 107, 107, 107], 10, 10, "1d", "30m", "binary_tree"),  
            ([93, 107, 107, 107], 10, 10, "1d", "30m", "star"),  
            ([93, 107, 107, 107], 10, 10, "1d", "30m", "grid"),  
        ]
    )
    @pytest.mark.quarantined
    def test_process_dags_queries_count(