TASK: Drop remnants of dnf-4

[yselkowitz]

What does the ELN SIG need to do?

DNF5 is the default package manager in Fedora 41, and now in ELN (#201). At the same time, dnf-4, libdnf, etc. will see less maintenance, and therefore should also be dropped prior to RHEL 11. However, getting rid of those will take more work, mostly beyond our scope:

• anaconda needs to be ported to python3-libdnf5
• kpatch-dnf (RHEL-specific) needs to be ported to python3-libdnf5
• Switch osbuild to use python3-libdnf5 instead of python3-libdnf: spec: use python3-libdnf5 in RHEL 11 and ELN osbuild/osbuild#1894
• PackageKit needs to be ported to libdnf5
• policycoreutils(-devel) needs to be ported to python3-libdnf5
• subscription-manager needs to be ported to python3-libdnf5

Trackers:
https://tiny.distro.builders/view-rpm--view-eln--python3-dnf.html
https://tiny.distro.builders/view-rpm--view-eln--python3-dnf-plugins-core.html

[yselkowitz]

Also, Content Resolver is still using python3-dnf from dnf-4, so that too should be ported to python3-libdnf5: minimization/content-resolver#75

[yselkowitz]

RHBZ tracker: https://bugzilla.redhat.com/show_bug.cgi?id=DNF5 (thanks @michel-slm)