drop debug printf

Index: src/vala/gmpc-metadata-editwindow.vala
--- src/vala/gmpc-metadata-editwindow.vala.orig
+++ src/vala/gmpc-metadata-editwindow.vala
@@ -183,7 +183,6 @@ public class Gmpc.MetaData.EditWindow : Gtk.Window
 
     public void callback(void *handle,string? plugin_name,GLib.List<MetaData.Item>? list)
     {
-        stdout.printf("result callback\n");
         bar.pulse();
         if(list == null)
         {
