doc: Switch to new IRC channel

See pytest-dev/pytest#8722

Author: The-Compiler

doc/_templates/indexsidebar.html

@@ -18,4 +18,4 @@ <h3>Questions? Suggestions?</h3>
 
 <p>Join <a href="http://mail.python.org/mailman/listinfo/execnet-dev">
   execnet-dev mailing list </a></p>
-<p>come to <tt>#pylib</tt> on FreeNode</p>
+<p>come to <tt>#pytest</tt> on Libera Chat</p>

doc/support.rst

@@ -7,7 +7,10 @@ are welcome to:
 * join `execnet-dev`_ for general discussions
 * join `execnet-commit`_ to be notified of changes
 * clone the `github repository`_ and submit patches
-* hang out on the irc.freenode.net #pylib channel
+* hang out on the #pytest channel `on irc.libera.chat
+<ircs://irc.libera.chat:6697/#pytest>`_ (using an IRC client, `via webchat
+<https://web.libera.chat/#pytest>`_, or `via Matrix
+<https://matrix.to/#/%23pytest:libera.chat>`_).
 * follow the `tetamap blog`_ or `Holger's twitter presence`_.
 * contact merlinux_ if you want to buy teaching or other support.