RFC: drop --cpu-rt-period and --cpu-rt-runtime flags?

With podman 6 we dropped cgroupv2 support but we never removed the --cpu-rt-period and --cpu-rt-runtime cli options. As documented they only work on a cgroupsv1 system.

It does not make sense to have options that cannot work anymore since running on cgroupv1 returns a hard error. However currently the options only print a warning not a hard error, so technically removing them would break whoever set them since they only saw a warning before.

https://github.com/podman-container-tools/podman/blob/f1b80e51215f8edb6f8e01929685339e94a8ae72/pkg/specgen/generate/validate_linux.go#L55-L65

While I would not think anyone would set them on a v2 system I guess it is best to avoid this breaking change right now and defer full removal for podman 7.

That said I guess at minimum right now we should remove the docs and hide the flags