The comment serialization for the screenshot review UI was a bit broken, trying to pull the wrong keys out of the serialized comment dict. This change fixes that, and updates it so we're using our standard region comment serialization types for everything. Testing Done: Created a review request with a screenshot via the admin DB forms. Added a comment to that screenshot and published the review. Reopened the review UI and saw that the comment was properly loaded back into the review UI without any errors.