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/models/test_taskinstance.py
now = pendulum.now('Europe/Brussels')
        dag = DAG('dag', start_date=DEFAULT_DATE)
        task = DummyOperator(task_id='op', dag=dag)
        ti = TI(task=task, execution_date=now)
        query = urllib.parse.parse_qs(
            urllib.parse.urlparse(ti.mark_success_url).query, keep_blank_values=True, strict_parsing=True
        )
        assert query['dag_id'][0] == 'dag'
        assert query['task_id'][0] == 'op'
        assert pendulum.parse(query['execution_date'][0]) == now
    def test_overwrite_params_with_dag_run_conf(self):
        task = DummyOperator(task_id='op')
        ti = TI(task=task, execution_date=datetime.datetime.now())
        dag_run = DagRun()
        dag_run.conf = {"override": True}
        params = {"override": False}
        ti.overwrite_params_with_dag_run_conf(params, dag_run)
        assert params["override"] is True
    def test_overwrite_params_with_dag_run_none(self):
        task = DummyOperator(task_id='op')
        ti = TI(task=task, execution_date=datetime.datetime.now())
        params = {"override": False}
        ti.overwrite_params_with_dag_run_conf(params, None)
        assert params["override"] is False
    def test_overwrite_params_with_dag_run_conf_none(self):