update FAQ required open tcp ports

fixes bigbluebutton/bigbluebutton#9132

Author: basisbit

_posts/2015-04-05-faq.md

@@ -471,7 +471,7 @@ For the above reasons, we recommend you setup BigBlueButton on a dedicated serve
 
 ### What ports must be open for external users to connect to BigBlueButton
 
-For TCP ports, clients must be able to connect to the BigBlueButton server on port 80/443 (HTTP/HTTPS), 7443 (audio), and 1935 (RTMP).  
+For TCP ports, clients must be able to connect to the BigBlueButton server on port 80/443 (HTTP/HTTPS).  
 
 For UDP ports, clients must be able to connect on a port within the range 16384-32767 for WebRTC-based audio.