Updates

Author: azhar2005

articles/application-gateway/multiple-site-overview.md

@@ -35,6 +35,7 @@ The priority field only impacts the order of evaluation of a request routing rul
 
 >[!NOTE]
 >If you wish to use rule priority, you will have to specify rule-priority field values for all the existing request routing rules. Once the rule priority field is in use, any new routing rule that is created would also need to have a rule priority field value as part of its config.
+Starting with API version 2021-08-01 rule priority field would be a mandatory field as part of the request routing rules. 
 
 ## Wildcard host names in listener