as pointed out in concourse/concourse#5080, Fedora now ships with cgroupv2
enabled by default.

our current worker garden backend implementation (guardian) does not support
that though: folks running with cgroupv2 enabled should take actions to
downgrade to v1 first (see https://fedoraproject.org/wiki/Changes/CGroupsV2#Upgrade.2Fcompatibility_impact)

in our prerequisites, we don't mention that though:

https://concourse-ci.org/concourse-worker.html#worker-prerequisites

It'd be great to point folks out to a reference that helps them out with making
their sys compatible.

ps.: this might soon change with our use of containerd (as progress is made
on making containerd cgroupv2-ready).

refs:

• https://fedoraproject.org/wiki/Changes/CGroupsV2#Modify_Fedora_31_to_use_CgroupsV2_by_default
• https://github.com/cloudfoundry/garden
• https://github.com/cloudfoundry/guardian