fix(getting_started): Add timeout before enabling DAG

[NickLarsenNZ]

Without this, there is a high chance of hitting this error:

We have a healthy webserver!
Triggering a DAG run. Enable DAG...
{
  "detail": null,
  "status": 404,
  "title": "Dag with id: 'example_trigger_target_dag' not found",
  "type": "https://airflow.apache.org/docs/apache-airflow/2.10.5/stable-rest-api-ref.html#section/Errors/NotFound"
}
Checking DAG result ...
The DAG was not successful. State:  null