**Apache Airflow version**:

master

**Kubernetes version (if you are using kubernetes)** (use `kubectl version`):

**Environment**: breeze

**What happened**:

This DAG
```python
from airflow import models
from airflow.operators.dummy_operator import DummyOperator
from airflow.utils.dates import days_ago

with models.DAG("test", start_date=days_ago(1), schedule_interval=None,) as dag:
    t1 = DummyOperator(task_id="t1")
    t2 = DummyOperator(task_id="t2")
    t1 >> t2
```

is rendering like that:

<img width="1374" alt="Screenshot 2020-08-27 at 19 59 41" src="https://user-images.githubusercontent.com/9528307/91478403-11d7fb00-e8a0-11ea-91d0-d7d578bcb5a2.png">

**What you expected to happen**:

I expect to see same relations as defined in DAG file

**How to reproduce it**:

Render the example DAG from above.


**Anything else we need to know**:

I'm surprised by this bug 👀 

airflow/www/views.py
"""Deletes DAG."""
        from airflow.api.common.experimental import delete_dag
        from airflow.exceptions import DagFileExists, DagNotFound
        dag_id = request.values.get('dag_id')
        origin = get_safe_url(request.values.get('origin'))
        try:
            delete_dag.delete_dag(dag_id)
        except DagNotFound:
            flash("DAG with id {} not found. Cannot delete".format(dag_id), 'error')
            return redirect(request.referrer)
        except DagFileExists:
            flash("Dag id {} is still in DagBag. "
                  "Remove the DAG file first.".format(dag_id),
                  'error')
            return redirect(request.referrer)
        flash("Deleting DAG with id {}. May take a couple minutes to fully"
              " disappear.".format(dag_id))
        
        return redirect(origin)
    @expose('/trigger', methods=['POST', 'GET'])
    @has_dag_access(can_dag_edit=True)
    @has_access
    @action_logging
    @provide_session
    def trigger(self, session=None):