Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/DocumentFragment.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 DocumentFragment
-interface DocumentFragment extends Element default _DocumentFragmentFactoryProvider {
-
-  DocumentFragment();
-
-  DocumentFragment.html(String html);
-
-  // TODO(nweiz): enable this when XML is ported
-  // /** WARNING: Currently this doesn't work on Dartium (issue 649). */
-  // DocumentFragment.xml(String xml);
-
-  DocumentFragment.svg(String svg);
-
-  DocumentFragment clone(bool deep);
-
-
-  /**
-   * @domName EventTarget.addEventListener, EventTarget.removeEventListener, EventTarget.dispatchEvent
-   */
-  ElementEvents get on();
-
-  /** @domName DocumentFragment.querySelector */
-  Element $dom_querySelector(String selectors);
-
-  /** @domName DocumentFragment.querySelectorAll */
-  NodeList $dom_querySelectorAll(String selectors);
-
-}