add region tags (#5028)

Author: leahecole

composer/workflows/airflow_db_cleanup.py

@@ -11,6 +11,8 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
+# [START composer_metadb_cleanup]
 """
 A maintenance workflow that you can deploy into Airflow to periodically clean
 out the DagRun, TaskInstance, Log, XCom, Job DB and SlaMiss entries to avoid
@@ -383,3 +385,5 @@ def cleanup_function(**context):
         dag=dag)
 
     print_configuration.set_downstream(cleanup_op)
+
+# [END composer_metadb_cleanup]