Base: Clarify that TelnetServer must be run as root

Author: https://github.com/SuperSonicHub1
Commit: 3b61fbf15f
Pull-request: https://github.com/SerenityOS/serenity/pull/12245
Reviewed-by: https://github.com/alimpfard

Base/usr/share/man/man8/TelnetServer.md

@@ -10,7 +10,8 @@ $ TelnetServer [-p port] [-c command]
 ## Description
 
 TelnetServer is a basic telnet server for Serenity. By default, it
-runs on port 23 and provides a shell upon connection.
+runs on port 23 and provides a shell upon connection. This program
+must be run as root.
 
 ## Options