remove keep above since parent now works

src/main-window.vala

@@ -78,7 +78,6 @@ namespace Sernatur {
 		private void menu_tours(Gtk.MenuItem menu_item) {
 			tour_window = new TourWindow (application);
 			tour_window.set_transient_for (this); // Set this window as the parent of the new window
-			tour_window.set_keep_above (true);
 			tour_window.present ();
 		}