Remove the replace directive and update x/tools.

For golang/go#63220

Change-Id: I1dcffde979bf17ee84df7003c0d13d6933072300
Reviewed-on: https://go-review.googlesource.com/c/tools/+/534398
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Robert Findley <rfindley@google.com>