fix unmatched region tag (GoogleCloudPlatform#4581)

Thank you @tmatsuo and snippets bot!!!

Author: leahecole

composer/workflows/hadoop_tutorial.py

@@ -103,4 +103,4 @@
     create_dataproc_cluster >> run_dataproc_hadoop >> delete_dataproc_cluster
     # [END composer_hadoop_steps]
 
-# [END composer_hadoop]
+# [END composer_hadoop_tutorial]