### Apache Airflow version

2.2.0 (latest released)

### Operating System

Mac

### Versions of Apache Airflow Providers

_No response_

### Deployment

Other Docker-based deployment

### Deployment details

_No response_

### What happened

Getting an exception when returning None from next_dagrun_info in a custom timetable. The timetable protocol says that when None is returned a DagRun will not happen but right now it throws an exception.

Exception:
```
Traceback (most recent call last):
  File "/home/airflow/.local/lib/python3.9/site-packages/airflow/jobs/scheduler_job.py", line 623, in _execute
    self._run_scheduler_loop()
  File "/home/airflow/.local/lib/python3.9/site-packages/airflow/jobs/scheduler_job.py", line 704, in _run_scheduler_loop
    num_queued_tis = self._do_scheduling(session)
  File "/home/airflow/.local/lib/python3.9/site-packages/airflow/jobs/scheduler_job.py", line 787, in _do_scheduling
    callback_to_run = self._schedule_dag_run(dag_run, session)
  File "/home/airflow/.local/lib/python3.9/site-packages/airflow/jobs/scheduler_job.py", line 1039, in _schedule_dag_run
    self._update_dag_next_dagruns(dag, dag_model, active_runs)
  File "/home/airflow/.local/lib/python3.9/site-packages/airflow/jobs/scheduler_job.py", line 930, in _update_dag_next_dagruns
    data_interval = dag.get_next_data_interval(dag_model)
  File "/home/airflow/.local/lib/python3.9/site-packages/airflow/models/dag.py", line 629, in get_next_data_interval
    return self.infer_automated_data_interval(dag_model.next_dagrun)
  File "/home/airflow/.local/lib/python3.9/site-packages/airflow/models/dag.py", line 671, in infer_automated_data_interval
    raise ValueError(f"Not a valid timetable: {self.timetable!r}")
ValueError: Not a valid timetable: <my_timetables.workday_timetable.WorkdayTimetable object at 0x7f42b1f02430>
```

### What you expected to happen

DagRun to not happen.

### How to reproduce

Create a custom timetable and return None in next_dagrun_info after a few DagRuns are created by that timetable

### Anything else

_No response_

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

tests/models/test_dag.py
"""
        Tests following_schedule a dag with a relativedelta schedule_interval
        """
        dag_id = "test_schedule_dag_relativedelta"
        delta = relativedelta(hours=+1)
        dag = DAG(dag_id=dag_id, schedule_interval=delta)
        dag.add_task(BaseOperator(task_id="faketastic", owner='Also fake', start_date=TEST_DATE))
        _next = dag.following_schedule(TEST_DATE)
        assert _next.isoformat() == "2015-01-02T01:00:00+00:00"
        _next = dag.following_schedule(_next)
        assert _next.isoformat() == "2015-01-02T02:00:00+00:00"
    def test_previous_schedule_datetime_timezone(self):
        
        start = datetime.datetime(2018, 3, 25, 2, tzinfo=datetime.timezone.utc)
        dag = DAG('tz_dag', start_date=start, schedule_interval='@hourly')
        when = dag.previous_schedule(start)
        assert when.isoformat() == "2018-03-25T01:00:00+00:00"
    def test_following_schedule_datetime_timezone(self):
        
        start = datetime.datetime(2018, 3, 25, 2, tzinfo=datetime.timezone.utc)
        dag = DAG('tz_dag', start_date=start, schedule_interval='@hourly')
        when = dag.following_schedule(start)
        assert when.isoformat() == "2018-03-25T03:00:00+00:00"
    def test_following_schedule_datetime_timezone_utc0530(self):
        
        class UTC0530(datetime.tzinfo):