Update understand-guidelines-active-directory-domain-service-site.md

typo in the AD port - see: https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/service-overview-and-network-port-requirements#:~:text=Ports-,Active%20Directory%20Web%20Services%20(ADWS),9389,-Active%20Directory%20Management

Author: MaxMelcher

articles/azure-netapp-files/understand-guidelines-active-directory-domain-service-site.md

@@ -41,7 +41,7 @@ The required network ports are as follows:
 
 | Service | Port | Protocol |
 | -- | - | - |
-|AD Web Services | 9839 | TCP |
+|AD Web Services | 9389 | TCP |
 | DNS* | 53 | TCP |
 | DNS* | 53 | UDP |
 | ICMPv4 | N/A | Echo Reply |