Remove the replace directive and update x/tools.

For golang/go#54421

Change-Id: I66591a3c8ca2491243d6bec14b2d8b2f7ede237b
Reviewed-on: https://go-review.googlesource.com/c/tools/+/422905
Run-TryBot: Robert Findley <[email protected]>
Reviewed-by: Suzy Mueller <[email protected]>
gopls-CI: kokoro <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>