Update golang.org/x dependencies to their latest tagged versions.

Change-Id: If9b44decd91eb9cf6e5541ee75aff761d3a46a8b
Reviewed-on: https://go-review.googlesource.com/c/tools/+/590415
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>