Update x/tools.

For golang/go#65964

Change-Id: I0cebc18326d1b2c0949c0a8583d761bd22f737d0
Reviewed-on: https://go-review.googlesource.com/c/tools/+/567419
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>
Auto-Submit: Robert Findley <[email protected]>