switch irc channel

docs/mainpage.dox

@@ -53,7 +53,7 @@ The <a class="el" href="http://lists.cubik.org/mailman/listinfo/enet-discuss">en
 /**
 @page IRCChannel IRC Channel
 
-Join the \#enet channel on the <a class="el" href="http://freenode.net">freenode IRC network (irc.freenode.net)</a> for real-time discussion about the ENet library.
+Join the \#enet channel on the <a class="el" href="https://libera.chat">Libera Chat IRC network (irc.libera.chat)</a> for real-time discussion about the ENet library.
 
 */