Updated the off-boarding process

Why is this change being made?

The off-boarding page has some tasks assigned to the People Ops that are currently not completed by this team. Seeing that the handbook is the SSOT, this MR is to indicate the right task owners. Should there be plans to move these tasks to the People Ops team, we will come back and update the handbook to reflect this.

@gl-people-exp please feel free to review and update if need be.

@gl-peoplepartners kindly take note

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)