Update IRC information

Author: headius

chat.markdown

@@ -9,4 +9,5 @@ Most of the JRuby team and much of the community hangs out on Matrix, and we wel
 To join, visit the [Matrix #jruby room](https://matrix.to/#/#jruby:matrix.org) and select a client that suits you. The
 [Matrix #jruby logs](https://view.matrix.org/alias/%23jruby:matrix.org) are also publically readable.
 
-Many of the core JRuby committers also hang out on [Gitter](https://gitter.im/jruby/jruby). The Matrix room also bridges to the #jruby channel on [Freenode IRC](https://freenode.net).
+The Matrix room also bridges to the #jruby channel on [Libera IRC](https://libera.chat).
+