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/+/167385Reviewed-by: Bryan C. Mills <bcmills@google.com>

src/cmd/go/internal/work/build.go

@@ -10,7 +10,6 @@ import (
 	"go/build"
 	"os"
 	"os/exec"
-	//"path"
 	"path/filepath"
 	"runtime"
 	"strings"