Revert "Merge branch '56850-add-new-unicorn-metrics' into 'master'"

What does this MR do?

This reverts https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/27474 due to performance issues. See https://gitlab.com/gitlab-org/gitlab-ce/issues/61964#note_171657074

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content