Updating steps and process for career mobility issues

We are working with our internal auditors to clarify the scope and requirements of the career mobility issues. Now that we've. determined scope of control we need to update the handbook to reflect these changes.

Author Checklist

• 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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• If the changes affect team members, or warrant an announcement in another way, please consider posting an update in #whats-happening-at-gitlab linking to this MR
  • If this is a change that directly impacts the majority of global team members, it should be a candidate for #company-fyi. Please work with internal communications and check the handbook for examples.

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