[gtkmm-documentation] Update a comment

[Murray Cumming <murrayc src gnome org>]

commit 5112dfa9a95ccc35b90150cf66f67fd4b54a0c07
Author: Murray Cumming <murrayc murrayc com>
Date:   Tue Apr 8 10:00:49 2014 +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 97e3aa1..87c5e43 100644
--- a/examples/book/application/app_and_win_menus/exampleapplication.cc
+++ b/examples/book/application/app_and_win_menus/exampleapplication.cc
@@ -61,7 +61,7 @@ void ExampleApplication::on_startup()
   submenu_edit->append("_Cut", "win.cut");
   Glib::RefPtr<Gio::MenuItem> item = Gio::MenuItem::create("_Copy", "win.copy");
   //Setting "accel" works, but might be deprecated soon: See 
https://bugzilla.gnome.org/show_bug.cgi?id=708908
-  //When it is deprecated, use Gtk::Application::add_accelerator() instead.
+  //When it is deprecated, use Gtk::Application::set_accel_for_action() instead.
   item->set_attribute_value("accel", Glib::Variant<Glib::ustring>::create("<Primary>c"));
   submenu_edit->append_item(item);
   item = Gio::MenuItem::create("_Paste", "win.paste");