cmd/go/internal/work: remove commented-out import

Somebody wasn't using goimports. :)

Change-Id: Ibad3c0781ea70d538592b2e90d8b578e4fae8173
Reviewed-on: https://go-review.googlesource.com/c/go/+/167385


Reviewed-by: Bryan C. Mills <bcmills@google.com>