The `go mod tidy` errors have been pointing to an older URL. This CL
fixes the URL by pointing to the correct URL: https://go.dev/ref/mod.
Fixes #49394
Change-Id: I707dda407ba032db8a55083998002a5ab72033e8
Reviewed-on: https://go-review.googlesource.com/c/go/+/633421 Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Sean Liao <sean@liao.dev> Reviewed-by: Michael Matloob <matloob@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>