treewide: use liberachat and OFTC in examples

Freenode was taken over by a wannabe bitcoin millionaire [1], which
prompted the migration of communities to Libera Chat and OFTC [2].

[1] https://blog.bofh.it/debian/id_461
[2] https://hackaday.com/2021/05/20/freenode-debacle-prompts-staff-exodus-new-network/

tests/modules/programs/hexchat/basic-configuration-expected-serverlist-config

@@ -8,7 +8,7 @@ S=irc.mzima.net
 S=irc.prison.net
 J=#computers
 
-N=freenode
+N=oftc
 L=6
 E=UTF-8 (Unicode)
 F=12
@@ -17,8 +17,6 @@ i=user_
 R=real_user
 U=user
 P=password
-S=chat.freenode.net
-S=irc.freenode.net
+S=irc.oftc.net
 J=#home-manager
-J=#nixos