mdns: documentation: fixed inconsistent enum in example of reading mdns results

* Original commit: espressif/esp-idf@786f5641f7

docs/en/api-reference/protocols/mdns.rst

@@ -126,7 +126,7 @@ Example method to resolve local services::
             }
             a = r->addr;
             while(a){
-                if(a->addr.type == MDNS_IP_PROTOCOL_V6){
+                if(a->addr.type == IPADDR_TYPE_V6){
                     printf("  AAAA: " IPV6STR "\n", IPV62STR(a->addr.u_addr.ip6));
                 } else {
                     printf("  A   : " IPSTR "\n", IP2STR(&(a->addr.u_addr.ip4)));