Remove IRC from README

Nobody's using it anymore

README.md

@@ -23,9 +23,6 @@ production.
     * [JavaScript API](https://remotestoragejs.readthedocs.io/en/latest/js-api.html)
     * [Usage with Node.js](https://remotestoragejs.readthedocs.io/en/latest/nodejs.html)
 * Ask questions on the [community forums](https://community.remotestorage.io/)
-* Ask questions on IRC in [#remotestorage on Libera.Chat](ircs://irc.libera.chat:6697/remotestorage)
-  ([Web Chat](https://web.libera.chat/#remotestorage))
-  (wait a bit, if nobody's responding right away)
 * If you found a potential bug, or want to propose a change, [open an issue on
   GitHub](https://github.com/remotestorage/remotestorage.js/issues). New issues
   will usually receive a response within 24-48 hours.