Drop irc channel from README.md, as we no longer use it.
Just discord now.
@@ -27,5 +27,4 @@ For guidelines on contributing, please see [CONTRIBUTING.md](https://github.com/
Contact
-------
-* Discord: https://discord.gg/7CPPzab
-* IRC: [#omf](http://webchat.freenode.net?channels=omf) on [irc.freenode.net](irc://chat.freenode.net/omf) !
+Discord: https://discord.gg/7CPPzab
