Remove the replace directive and update x/tools.

For golang/go#61926

Change-Id: I80f8f58592f06aba3a91896959fc2481ca3fc563
Reviewed-on: https://go-review.googlesource.com/c/tools/+/518377
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Peter Weinberger <pjw@google.com>