Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/SVGElement.dartdoc

-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-/// @domName SVGElement
-interface SVGElement extends Element default _SVGElementFactoryProvider {
-
-  SVGElement.tag(String tag);
-  SVGElement.svg(String svg);
-
-  SVGElement clone(bool deep);
-
-
-  /** @domName SVGElement.id */
-  String id;
-
-  /** @domName SVGElement.ownerSVGElement */
-  final SVGSVGElement ownerSVGElement;
-
-  /** @domName SVGElement.viewportElement */
-  final SVGElement viewportElement;
-
-  /** @domName SVGElement.xmlbase */
-  String xmlbase;
-
-}