cmd/go/internal/cfg: remove unused Gopath variable

Change-Id: Ib268157674824fd7552d3c36a61eccf8c720eaeb
Reviewed-on: https://go-review.googlesource.com/c/go/+/167083
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/go/internal/cfg/cfg.go

@@ -73,7 +73,6 @@ var (
 	Goarch    = BuildContext.GOARCH
 	Goos      = BuildContext.GOOS
 	ExeSuffix string
-	Gopath    = filepath.SplitList(BuildContext.GOPATH)
 
 	// ModulesEnabled specifies whether the go command is running
 	// in module-aware mode (as opposed to GOPATH mode).