{HDInsight} az hdinsight application: Add declaration of unusable versions due to deprecation of Api-version 2018-06-01-preview (#30661)

* Update

* Update

* Update

---------

Co-authored-by: v-yuchenli <v-yuchenli@microsoft.com>

Author: yuc-Li

src/azure-cli/azure/cli/command_modules/hdinsight/_help.py

@@ -16,6 +16,7 @@
 helps['hdinsight application'] = """
 type: group
 short-summary: Manage HDInsight applications.
+long-summary: We no longer maintain module before version 2.30.0. It is recommended to upgrade to at least version 2.30.0.
 """
 
 helps['hdinsight application create'] = """