We don't use IRC anymore

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

.github/config.yml

@@ -1,5 +1,3 @@
 firstPRMergeComment: >
     Thanks for your first pull request and welcome to the community!
     Feel free to keep them coming! If you are looking for issues to tackle then have a look at this selection: https://github.com/nextcloud/server/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22
-
-    Most developers hang out on IRC. So join \#nextcloud-dev on Freenode for a chat!