Update Compaas instructions for FY23 annual comp review.

Why is this change being made?

Updating the Compaas instructions with refreshed information on how to use Compaas and what slate owners and approvers can expect to find in Compaas for the FY23 cycle. I'm hoping this is a good start to help clarify how Compaas will be used for this cycle with refreshed screenshots and further clarification to follow once our cycle is loaded into the tool.

cc @gl-total-rewards @gl-peoplepartners

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
  • Copy/paste the Slack conversation to document it for later, or upload screenshots. Verify that no confidential data is added.
• Assign reviewers for this change to the correct DRI(s)
  • 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 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.

---