cmd/pack,vet: use `go doc` instead of `godoc` in doc

Change-Id: Ic5f62a7d0a5c090da69213d1d0187af0ea48e358
Reviewed-on: https://go-review.googlesource.com/20820Reviewed-by: Rob Pike <r@golang.org>

src/cmd/pack/pack.go

@@ -40,7 +40,7 @@ For compatibility with old Go build environments the op string grc is
 accepted as a synonym for c.
 
 For more information, run
-	godoc cmd/pack`
+	go doc cmd/pack`
 
 func usage() {
 	fmt.Fprintln(os.Stderr, usageMessage)

src/cmd/vet/main.go

@@ -164,7 +164,7 @@ func Usage() {
 	fmt.Fprintf(os.Stderr, "\tvet [flags] directory...\n")
 	fmt.Fprintf(os.Stderr, "\tvet [flags] files... # Must be a single package\n")
 	fmt.Fprintf(os.Stderr, "For more information run\n")
-	fmt.Fprintf(os.Stderr, "\tgodoc cmd/vet\n\n")
+	fmt.Fprintf(os.Stderr, "\tgo doc cmd/vet\n\n")
 	fmt.Fprintf(os.Stderr, "Flags:\n")
 	flag.PrintDefaults()
 	os.Exit(2)