Remove the replace directive and update x/tools.

For golang/go#64973

Change-Id: Ia5ae53c8e1ed415b417bd2be125a0077d9a0c319
Reviewed-on: https://go-review.googlesource.com/c/tools/+/562038
Reviewed-by: Suzy Mueller <suzmue@golang.org>
Auto-Submit: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>