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

Change-Id: Icc6dd9750a9b5fabba1977e9921171fd2ea1a63b
Reviewed-on: https://go-review.googlesource.com/c/vuln/+/764903
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>