chore(dynamo): fix default template example

rel/i18n/emqx_bridge_dynamo.hocon

@@ -37,7 +37,7 @@ local_topic.label:
 template.desc:
 """Template, the default value is empty. When this value is empty the whole message will be stored in the database.<br>
 The template can be any valid json with placeholders and make sure all keys for table are here, example:<br>
-  {"id" : ${id}, "clientid" : ${clientid}, "data" : ${payload}}"""
+  {"id" : "${id}", "clientid" : "${clientid}", "data" : "${payload.data}"}"""
 
 template.label:
 """Template"""