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 <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>