The note entitled "Repository URL changes" from 2015/04/25 should be removed from repos.gentoo.org. This is long since expired as a 'recent change' item. Reproducible: Always
I've updated the template in commit 8878350cd6061cebd9c63cc406c5f4ffd792ffd8 (of infra puppet repo). I hope in some time it would propagate across CDN and caches and show without that warning.