**Apache Airflow version**: 2.1.0

**What happened**:

We use a python script that reads JSON configs from db to dynamically generate DAGs. Sometimes, when JSON Configs is updated, we expect DAGs to be removed in Airflow.  This doesn't always happen. From my observation, one of the following happens:
1) DAG is removed because the python script no longer generates it.
2) DAG still exists but run history is empty. When trigger the DAG, first task is stuck in `queued` status indefinitely.

**What you expected to happen**:
I expect the right behavior should be 
>1) DAG is removed because the python script no longer generates it.

**How to reproduce it**:
* Create a python script in DAG folder that dynamically generates multiple DAGs
* Execute these dynamically generated DAGs a few times
* Use Airflow Variable to toggle (reduce) the # of DAGs generated
* Examine if number of dynamically generated DAGs in the web UI


airflow/models/dag.py
DagContext.push_context_managed_dag(self)
        return self
    def __exit__(self, _type, _value, _tb):
        DagContext.pop_context_managed_dag()
    
    @staticmethod
    def _upgrade_outdated_dag_access_control(access_control=None):
        """
        Looks for outdated dag level actions (can_dag_read and can_dag_edit) in DAG
        access_controls (for example, {'role1': {'can_dag_read'}, 'role2': {'can_dag_read', 'can_dag_edit'}})
        and replaces them with updated actions (can_read and can_edit).
        """
        if not access_control:
            return None
        new_perm_mapping = {
            permissions.DEPRECATED_ACTION_CAN_DAG_READ: permissions.ACTION_CAN_READ,
            permissions.DEPRECATED_ACTION_CAN_DAG_EDIT: permissions.ACTION_CAN_EDIT,
        }
        updated_access_control = {}
        for role, perms in access_control.items():
            updated_access_control[role] = {new_perm_mapping.get(perm, perm) for perm in perms}
        if access_control != updated_access_control:
            warnings.warn(
                "The 'can_dag_read' and 'can_dag_edit' permissions are deprecated. "
                "Please use 'can_read' and 'can_edit', respectively.",
                DeprecationWarning,
                stacklevel=3,
            )
        return updated_access_control
    def date_range(