Update CEO scoring items

Why is this change being made?

With linked items, we want to update the guidance on how to add division/team OKRs to CEO KRs so that it's easy to see all items that contribute to a CEO OKR.

Two methods are outlined to ensure that scoring can be updated either manually or automatically. To update manually, at this time, the OKR must have no children.

A bunch of the existing wording was removed to keep the content focused on what GitLab team members need to know.

Checkins are also coming, so a small note is included in this MR.

Example of how I expect it to look (with method 1):

Note: This was created for example purposes only and does not reflect the status at any point in time.

Author and Reviewer Checklist

Please verify the check list and ensure to tick them off before the MR is merged.

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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  • The when to get approval handbook section explains the workflow in more detail
• For transparency, share this MR with the audience that will be impacted.
  • Team: For changes that affect your direct team, share in your group Slack channel
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