community/cgmanager: drop
The repository has been archived upstream for 5 years, and main page[1] has a note that says:
Note
CGManager was used by default with LXC in Ubuntu since April 2014 and then by other distributions as they started needing working unprivileged containers.
It has now been deprecated in favor of the CGroup namespace in recent Linux kernels. On older kernels, LXCFS still offers a cgroupfs emulation that can be used instead of CGManager and is more widely compatible with existing userspace.
[1] https://linuxcontainers.org/cgmanager/
So let's drop the package, should certainly not be something we need in alpine 3.21