[gtkmm-documentation] Update a comment

[Murray Cumming <murrayc src gnome org>]

commit ccca9b3a73b2dee98737ee4f84216753c8c1f008
Author: Murray Cumming <murrayc murrayc com>
Date:   Tue Oct 1 11:39:55 2013 +0200

    Update a comment

 .../app_and_win_menus/exampleapplication.cc        |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/examples/book/application/app_and_win_menus/exampleapplication.cc 
b/examples/book/application/app_and_win_menus/exampleapplication.cc
index efed650..c823763 100644
--- a/examples/book/application/app_and_win_menus/exampleapplication.cc
+++ b/examples/book/application/app_and_win_menus/exampleapplication.cc
@@ -60,7 +60,7 @@ void ExampleApplication::on_startup()
   Glib::RefPtr<Gio::Menu> submenu_edit = Gio::Menu::create();
   submenu_edit->append("_Cut", "win.cut");
   Glib::RefPtr<Gio::MenuItem> item = Gio::MenuItem::create("_Copy", "win.copy");
-  //TODO: This works, but doesn't seem to be documented. See 
https://bugzilla.gnome.org/show_bug.cgi?id=708908
+  //Setting "accel" works, but might be deprecated soon: See 
https://bugzilla.gnome.org/show_bug.cgi?id=708908
   item->set_attribute_value("accel", Glib::Variant<Glib::ustring>::create("<Primary>c"));
   submenu_edit->append_item(item);
   item = Gio::MenuItem::create("_Copy", "win.paste");