[release-branch.go1.14] cmd: update golang.org/x/tools to v0.0.0-20200602230032-c00d67ef29d0

This teaches vet to recognize %O in a fmt.Printf format string.
O has been supported since the 1.13 release, but vet would warn about it.

Fixes #39288.
For #29986.

Change-Id: Ia7817ee60ae6beac32cc402c0c68afa917e4ef0f
Reviewed-on: https://go-review.googlesource.com/c/go/+/236199


Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>