remove unused media id part, it's been build in download video automatically

mediaId.go

@@ -71,13 +71,10 @@ func getMediaPostURL(t string) (url string, err error) {
 func saveMedia2File(mediaID string) (filename string, err error) {
 
 	url := mediaID2URL(mediaID)
-	file, t, e := saveURL(url)
+	file, _, e := saveURL(url)
 	if e != nil {
 		return "", e
 	}
-	if t == "json" {
-		fmt.Println("get json should be video")
-	}
 	fmt.Println("save media to " + file)
 
 	return file, nil