Drop Fedora 40 support

[almet]

Security support for Fedora 40 ended 4 weeks ago (13 May 2025), so we could remove it in the next release.

This mainly means:

• Updating the documentation ;
• Updating the CI checks ;
• Potentially removing the F40 packages from our yum-tools-prod repository, potentially grouping with the move to the R2 infrastructure there.