Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/StyleElement.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 HTMLStyleElement
-interface StyleElement extends Element default _Elements {
-
-  StyleElement();
-
-  /** @domName HTMLStyleElement.disabled */
-  bool disabled;
-
-  /** @domName HTMLStyleElement.media */
-  String media;
-
-  /** @domName HTMLStyleElement.scoped */
-  bool scoped;
-
-  /** @domName HTMLStyleElement.sheet */
-  final StyleSheet sheet;
-
-  /** @domName HTMLStyleElement.type */
-  String type;
-}