Update Code Review CM to Complete

Why is this change being made?

In FY21-Q2 we completed a Category Maturity Scorecard to validate the “Lovable” maturity of the Code Review category, based on user performance. After research, the revised maturity is now “Complete”.

This MR updates the Code Review category by:

• Setting the current maturity to complete.
• Setting that the category is now using the new_maturity methodology.
• Updating the target date to move the maturity back to lovable

References

• Research issue: https://gitlab.com/gitlab-org/ux-research/-/issues/941
• Research data and insights: Dovetail project

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][transparency]
• Assign this change to the correct DRI
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to your manager.
  • 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][mr-buddies-slack].
  • 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.