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

Change-Id: I993c77edbea8426f558ab84c4ba769e0bdf6406d
Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/568935
Reviewed-by: Than McIntosh <thanm@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>