Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/LinkElement.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.
-
-// WARNING:
-//   This file contains documentation that is merged into the real source.
-//   Do not make code changes here.
-
-/// @domName HTMLLinkElement
-interface LinkElement extends Element default _Elements {
-
-  LinkElement();
-
-  /** @domName HTMLLinkElement.charset */
-  String charset;
-
-  /** @domName HTMLLinkElement.disabled */
-  bool disabled;
-
-  /** @domName HTMLLinkElement.href */
-  String href;
-
-  /** @domName HTMLLinkElement.hreflang */
-  String hreflang;
-
-  /** @domName HTMLLinkElement.media */
-  String media;
-
-  /** @domName HTMLLinkElement.rel */
-  String rel;
-
-  /** @domName HTMLLinkElement.rev */
-  String rev;
-
-  /** @domName HTMLLinkElement.sheet */
-  final StyleSheet sheet;
-
-  /** @domName HTMLLinkElement.sizes */
-  DOMSettableTokenList sizes;
-
-  /** @domName HTMLLinkElement.target */
-  String target;
-
-  /** @domName HTMLLinkElement.type */
-  String type;
-}