Update x/tools.

For golang/go#66197

Change-Id: I7143d1a371a2eed88186cb0c5cf7019a78931b5e
Reviewed-on: https://go-review.googlesource.com/c/tools/+/570756
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Alan Donovan <adonovan@google.com>