README.md: IRC channel #vallumd is now on OFTC

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>

Author: stintel

README.md

@@ -180,4 +180,4 @@ Vallumd uses syslog(3) for logging.
 Get involved
 ------------
 
-* Join the #vallumd IRC channel on chat.freenode.net
+* Join the #vallumd IRC channel on irc.oftc.net