app: Removed unused function

https://bugzilla.gnome.org/show_bug.cgi?id=707663

src/shell-app.c

@@ -771,25 +771,6 @@ shell_app_get_n_windows (ShellApp *app)
   return g_slist_length (app->running_state->windows);
 }
 
-static gboolean
-shell_app_has_visible_windows (ShellApp   *app)
-{
-  GSList *iter;
-
-  if (app->running_state == NULL)
-    return FALSE;
-
-  for (iter = app->running_state->windows; iter; iter = iter->next)
-    {
-      MetaWindow *window = iter->data;
-
-      if (meta_window_showing_on_its_workspace (window))
-        return TRUE;
-    }
-
-  return FALSE;
-}
-
 gboolean
 shell_app_is_on_workspace (ShellApp *app,
                            MetaWorkspace   *workspace)