[gtkmm] ActionGroup: Remove _IS_DEPRECATED

[Murray Cumming <murrayc src gnome org>]

commit f103cfff86392624be4cd2195967a0c7f990ee81
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed Oct 9 11:50:30 2013 +0200

    ActionGroup: Remove _IS_DEPRECATED
    
    I added this by mistake in a recent commit.

 gtk/src/actiongroup.hg |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/gtk/src/actiongroup.hg b/gtk/src/actiongroup.hg
index ea8e3ad..8358f62 100644
--- a/gtk/src/actiongroup.hg
+++ b/gtk/src/actiongroup.hg
@@ -30,7 +30,8 @@ _PINCLUDE(glibmm/private/object_p.h)
 #define GDK_DISABLE_DEPRECATION_WARNINGS 1
 #m4 _POP()
 
-_IS_DEPRECATED // This whole file is deprecated.
+//TODO: Deprecate this when we are ready. It is already deprecated in GTK+.
+//_IS_DEPRECATED // This whole file is deprecated.
 
 namespace Gtk
 {