Remove the replace directive and update x/tools.

For golang/go#63220

Change-Id: Ibf4114b41f34bc57c724e435e0faf031a082d8d8
Reviewed-on: https://go-review.googlesource.com/c/tools/+/533177
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>