Libera started requiring an account for the IP ranges of GH CI.
This currently results in the IRC notification job running for
more than one hour because the IRC client it uses doesn't
terminate properly after giving up and thus eats our CI minutes.
The patch disables the notifications for now until we figure out
a better way, either by registering a libera account for the bot
and supplying the credentials via secret or by changing to GH
webhooks to a publicly available service like pipe.pico.sh which
then can be listened to by our existing IRC bot.
They were also called for the 'master' and 'v0.5' branches of forks and are
not that helpful anyway because they just post the compare link and not the
title of the commits.
Additionally, they were also called whenever a PR was merged which already
has its own notification including a link to the PR.
