Sunsetting CentOS support

[Andreas Klebinger]

Hello devs, with CentOS 7 reaching EOL we are demoting it to a Tier 2
platform and will eventually drop support completely.

There are no immediate plans to stop supporting it, but we will not
allocate any more resources towards support for it and will likely drop
support completely should it break in the future.

We introduced support for Rocky Linux as replacement for CentOS some
time ago, so users who need a RHEL compatible GHC distribution should be
able to use GHC packaged for Rocky Linux instead without issues.

Best Regards
Andreas Klebinger