[release-branch.go1.13] Revert "cmd/go: add a Latest field to the output of...

[release-branch.go1.13] Revert "cmd/go: add a Latest field to the output of 'go mod download -json'"

This reverts CL 183841.

Updates #34533
Fixes #34679

Reason for revert: Introduced a significant performance regression for repos with many incompatible-version tags.

Change-Id: I75d7fd76e6e1a0902b114b00167b38439e0f8221
Reviewed-on: https://go-review.googlesource.com/c/go/+/198699


Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Katie Hockman <katie@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
(cherry picked from commit 961837de)
Reviewed-on: https://go-review.googlesource.com/c/go/+/199079