Remove the replace directive and update x/tools.

For golang/go#54397

Change-Id: I83f4d8aebcaa562c7e059304596d5b000e1cff17
Reviewed-on: https://go-review.googlesource.com/c/tools/+/422897
Run-TryBot: Robert Findley <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
gopls-CI: kokoro <[email protected]>
Reviewed-by: Jamal Carvalho <[email protected]>