[libsigc++2/variadic_mem_fun2] Remove unnecessary TODO comment.

[Murray Cumming <murrayc src gnome org>]

commit e7bf4bc7ff672e2532e1a7f15c0fb12a75f09a2f
Author: Murray Cumming <murrayc murrayc com>
Date:   Sat Mar 5 23:15:30 2016 +0100

    Remove unnecessary TODO comment.

 sigc++/functors/macros/mem_fun.h.m4 |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/sigc++/functors/macros/mem_fun.h.m4 b/sigc++/functors/macros/mem_fun.h.m4
index 1b2fb36..3be8be5 100644
--- a/sigc++/functors/macros/mem_fun.h.m4
+++ b/sigc++/functors/macros/mem_fun.h.m4
@@ -256,7 +256,7 @@ public:
   operator()(type_trait_take_t<T_arg>... _A_a) const
     { return (obj_.invoke().*(this->func_ptr_))(_A_a...); }
 
-//protected: TODO?
+//protected:
   // Reference to stored object instance.
   // This is the handler object, such as TheObject in void TheObject::signal_handler().
   T_limit_reference obj_;