Remove commented out code in GlobalHandles::Node.

src/global-handles.cc

Index: src/global-handles.cc
diff --git a/src/global-handles.cc b/src/global-handles.cc
index 95c5c82bc2d341fd4d9780c1eba8dcbb72e333c0..6bca87a0ea04e40e7411f7c05c3b0af4d4be271e 100644
--- a/src/global-handles.cc
+++ b/src/global-handles.cc
@@ -192,10 +192,6 @@ class GlobalHandles::Node {
     set_independent(true);
   }
 
-  // Callback accessor.
-  // TODO(svenpanne) Re-enable or nuke later.
-  // WeakReferenceCallback callback() { return callback_; }
-
   // Callback parameter accessors.
   void set_parameter(void* parameter) {
     DCHECK(IsInUse());