Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/CSSStyleSheet.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 CSSStyleSheet
-interface CSSStyleSheet extends StyleSheet {
-
-  /** @domName CSSStyleSheet.cssRules */
-  final CSSRuleList cssRules;
-
-  /** @domName CSSStyleSheet.ownerRule */
-  final CSSRule ownerRule;
-
-  /** @domName CSSStyleSheet.rules */
-  final CSSRuleList rules;
-
-  /** @domName CSSStyleSheet.addRule */
-  int addRule(String selector, String style, [int index]);
-
-  /** @domName CSSStyleSheet.deleteRule */
-  void deleteRule(int index);
-
-  /** @domName CSSStyleSheet.insertRule */
-  int insertRule(String rule, int index);
-
-  /** @domName CSSStyleSheet.removeRule */
-  void removeRule(int index);
-}