fix(dashboards): cgroup memory usage

What

Stop using the rate function on container_memory_usage_bytes

Why

container_memory_usage_bytes is a gauge, so we can't use the rate function since this will give us bogus information.

• Reference: https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/16240
• Dashboard: https://dashboards.gitlab.net/dashboard/snapshot/6zTOvDZ9VI0S4mhsl4fWwXZu1yK2KxaE