CONTRIBUTING: drop obsolete mailing list and IRC channel

Author: bgilbert

CONTRIBUTING.md

@@ -12,15 +12,6 @@ Origin (DCO). This document was created by the Linux Kernel community and is a
 simple statement that you, as a contributor, have the legal right to make the
 contribution. See the [DCO](DCO) file for details.
 
-# Email and Chat
-
-The project currently uses the general CoreOS email list and IRC channel:
-- Email: [coreos-dev](https://groups.google.com/forum/#!forum/coreos-dev)
-- IRC: #[coreos](irc://irc.freenode.org:6667/#coreos) IRC channel on freenode.org
-
-Please avoid emailing maintainers found in the MAINTAINERS file directly. They
-are very busy and read the mailing lists.
-
 ## Getting Started
 
 - Fork the repository on GitHub