Update x/tools.

For golang/go#64973

Change-Id: Icfc2f5327e0f2154e65fb366647078538bb4190f
Reviewed-on: https://go-review.googlesource.com/c/tools/+/564656
Reviewed-by: Alan Donovan <[email protected]>
Auto-Submit: Robert Findley <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>