Remove outdated ObjC-related comments from the IDL

Source/core/dom/Element.idl

 /*
  * Copyright (C) 2006, 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 17 matching lines @@
 
     [TreatReturnedNullStringAs=Null] DOMString getAttribute([Default=Undefined] optional DOMString name);
     [RaisesException, CustomElementCallbacks=Enable] void setAttribute([Default=Undefined] optional DOMString name,
                                      [Default=Undefined] optional DOMString value);
     [CustomElementCallbacks=Enable] void removeAttribute([Default=Undefined] optional DOMString name);
     [MeasureAs=ElementGetAttributeNode] Attr getAttributeNode([Default=Undefined] optional DOMString name); // Removed from DOM4.
     [RaisesException, CustomElementCallbacks=Enable, MeasureAs=ElementSetAttributeNode] Attr setAttributeNode([Default=Undefined, StrictTypeChecking] optional Attr newAttr); // Removed from DOM4.
     [RaisesException, CustomElementCallbacks=Enable, MeasureAs=ElementRemoveAttributeNode] Attr removeAttributeNode([Default=Undefined, StrictTypeChecking] optional Attr oldAttr); // Removed from DOM4.
     [PerWorldBindings] NodeList getElementsByTagName([Default=Undefined] optional DOMString name);
 
-    // For ObjC this is defined on Node for legacy support.
     [PerWorldBindings] readonly attribute NamedNodeMap     attributes;
     boolean            hasAttributes();
 
     // DOM Level 2 Core
 
      DOMString getAttributeNS([TreatNullAs=NullString,Default=Undefined] optional DOMString namespaceURI,
                                             [Default=Undefined] optional DOMString localName);
      [RaisesException, CustomElementCallbacks=Enable] void setAttributeNS([TreatNullAs=NullString,Default=Undefined] optional DOMString namespaceURI,
                                        [Default=Undefined] optional DOMString qualifiedName,
                                        [Default=Undefined] optional DOMString value);
@@ skipping 154 matching lines @@
     [NotEnumerable, EnabledAtRuntime=touch, PerWorldBindings] attribute EventHandler ontouchstart;
     [NotEnumerable, EnabledAtRuntime=touch, PerWorldBindings] attribute EventHandler ontouchmove;
     [NotEnumerable, EnabledAtRuntime=touch, PerWorldBindings] attribute EventHandler ontouchend;
     [NotEnumerable, EnabledAtRuntime=touch, PerWorldBindings] attribute EventHandler ontouchcancel;
     [NotEnumerable, PerWorldBindings] attribute EventHandler onwebkitfullscreenchange;
     [NotEnumerable, PerWorldBindings] attribute EventHandler onwebkitfullscreenerror;
 };
 
 Element implements ParentNode;
 Element implements ChildNode;