Follow-up: VSA remove legacy, hardcoded identifiers

The following discussion from !78470 (merged) should be addressed:

• @blabuschagne started a discussion:

  Question: Is there a plan to remove the duplication? If so, could we update the comment to include a link to the issue as per https://docs.gitlab.com/ee/development/code_comments.html?

Duplicated content is in app/assets/javascripts/analytics/shared/constants.js, METRICS_POPOVER_CONTENT constant.