fix: Replace DummyOperator by EmptyOperator as it was removed in Airflow 2.4.3

Author: sweb

docs/modules/airflow/examples/example-configmap.yaml

@@ -8,7 +8,7 @@ data:
     from datetime import datetime, timedelta
     from airflow import DAG
     from airflow.operators.bash import BashOperator
-    from airflow.operators.dummy import DummyOperator
+    from airflow.operators.empty import EmptyOperator
 
     with DAG(
         dag_id='test_airflow_dag',
@@ -19,7 +19,7 @@ data:
         tags=['example', 'example2'],
         params={"example_key": "example_value"},
     ) as dag:
-        run_this_last = DummyOperator(
+        run_this_last = EmptyOperator(
             task_id='run_this_last',
         )