Update TW group assignments

Why is this change being made?

This MR updates the stages.yml file with new TW group assignments, based on our current staffing. The affected stages are:

• Manage: groups temporarily assigned to other Technical Writers because of Mike Jang's departure; new TW hire in process.

• Growth: groups assigned to our new Technical Writer, Kati Paizee, who is currently onboarding. As her comfort and confidence grows, we'll discuss future assignments with leadership.

The MR also updates the backups for each Technical Writer to reflect the team changes.

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 one of the people listed in the "Maintained by" section in on the page being edited.
  • 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. (this requirement has been removed pending identification of a new DRI for the handbook)