Update golang.org/x dependencies to their latest tagged versions.
Once this CL is submitted, and post-submit testing succeeds on all
first-class ports across all supported Go versions, this repository
will be tagged with its next minor version.

Change-Id: Ie2c9be1584d1f27ee5d9e8c0639c1d074f4669d9
Reviewed-on: https://go-review.googlesource.com/c/tools/+/507839
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Gopher Robot <gobot@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Auto-Submit: Gopher Robot <gobot@golang.org>