html: update URL in comment
The comment contained a link that had a file name and ID that no longer existed, so change to the URL of the corresponding part of the latest page.
Change-Id: I74e0885aabf470facc39b84035f7a83fef9c6a8e
GitHub-Last-Rev:
5681c84d9f1029449da6860c65a1d9a128296e85
GitHub-Pull-Request: golang/go#36514
Reviewed-on: https://go-review.googlesource.com/c/go/+/214181
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>