Switch plantuml from kube_container_memory to kube_container_rss saturation point
See https://gitlab.com/gitlab-com/gl-infra/capacity-planning-trackers/gitlab-com/-/issues/1773#note_2028947459 for more detailed reasoning form @msmiley.
See https://gitlab.com/gitlab-com/gl-infra/capacity-planning-trackers/gitlab-com/-/issues/1773#note_2028947459 for more detailed reasoning form @msmiley.