The existing URL in comment points to an Alioth page which was
deprecated (and not working), so use the new Benchmarks Game URL.

Change-Id: Ifd694382a44a24c44acbed3fe1b17bca6dab998f
Reviewed-on: https://go-review.googlesource.com/136835Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>