cmd/pushback: add gddo repo

Change-Id: I23d29f0f10cf8fbf48eb6f247344f437e84db52b
Reviewed-on: https://go-review.googlesource.com/20313
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

cmd/pushback/pushback.go

@@ -42,6 +42,7 @@ var repos = []string{
 	"golang/crypto",
 	"golang/debug",
 	"golang/exp",
+	"golang/gddo",
 	"golang/go",
 	"golang/gofrontend",
 	"golang/image",