Deprecate gitaly cgroups old config

In gitaly!4520 (merged), we are using a new cgroups configuration in Gitaly. See https://docs.gitlab.com/ee/administration/gitaly/configure_gitaly.html#configure-cgroups-in-gitaly.

The following configs are to be deprecated:

gitaly['cgroups_count']

gitaly['cgroups_memory_limit']

gitaly['cgroups_memory_enabled]

gitaly['cgroups_cpu_enabled']