[Duplicate] Growth PI update for users added to namespaces - change to include sub-groups in calculation

All changes have been added to !66140 (merged)

Closing this as a duplicate.

---

Why is this change being made?

To further clarify the definition and align this PI with how we are managing users in the application today.

• Note If needed, please see the related issue for more context.

Review app: https://timhey-master-patch-43210.about.gitlab-review.app/handbook/product/performance-indicators/index.html#new-group-namespace-with-at-least-two-users-added

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
• Assign this change to the correct DRI
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to your manager.
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies.
  • If the changes relate to any part of the project other than updates to content and/or data files please make sure to ping @gl-static-site-editor in a comment for a review and merge. For example changes to .gitlab-ci.yml, JavaScript/CSS/Ruby code or the layout files.