math/big: replace dead link in a comment with link to an archive.org copy
Happy to use another service if web.archive.org isn't suitable.
Note: the original page redirects and then links to some nsfw content.
Change-Id: Ie93ca0c6aad871881f35b7e5609b96da5c14cfc0
GitHub-Last-Rev:
ced5a97eb5c1d954a04d4bb61d36d955ca45a6ab
GitHub-Pull-Request: golang/go#54857
Reviewed-on: https://go-review.googlesource.com/c/go/+/428236
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Keith Randall <khr@google.com>