Update application-gateway-faq.yml

Updating the faq based - https://msazure.visualstudio.com/One/_workitems/edit/16012795

Author: rnautiyal

articles/application-gateway/application-gateway-faq.yml

@@ -76,6 +76,9 @@ sections:
           ```
 
           For HTTP/2 connections to the frontend IP address on Application Gateway v2 SKU, the idle timeout is set to 180 seconds and is non-configurable.
+          
+      - question: Does Application Gateway reuse the TCP connection that is  established with backend server?
+        answer: Yes. Application Gateway reuses the existing TCP connections with backend server.
 
       - question: Can I rename my Application Gateway resource?
         answer: No. There is no way to rename an Application Gateway resource. You must create a new resource with a different name.