Update deprecated cgroups conf

What does this MR do?

While testing GitLab installation in memory constrained environment I followed the docs and notice this deprecations warning:

Deprecations:
* gitaly[‘cgroups_count’] has been deprecated since 15.1 and will be removed in 16.0. Use `gitaly[‘cgroups_repositories_count’]` instead.
* gitaly[‘cgroups_memory_enabled’] has been deprecated since 15.1 and will be removed in 16.0. Use `gitaly[‘cgroups_memory_bytes’] or gitaly[‘cgroups_repositories_memory_bytes’] instead.
* gitaly[‘cgroups_cpu_enabled’] has been deprecated since 15.1 and will be removed in 16.0. Use `gitaly[‘cgroups_cpu_shares’] or gitaly[‘cgroups_repositories_cpu_shares’] instead.

This MR updates examples to use the new syntax

Related issues

Checklist

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• Merge Request Title, and Description are up to date, accurate, and descriptive
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Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
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