Remove the replace directive and update x/tools.

For golang/go#61675

Change-Id: I5be0e93a779bee699af72e91dfbe95640532e9fc
Reviewed-on: https://go-review.googlesource.com/c/tools/+/514577
gopls-CI: kokoro <noreply+kokoro@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>