Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/Attr.dartdoc

Index: lib/html/doc/interface/Attr.dartdoc
diff --git a/lib/html/doc/interface/Attr.dartdoc b/lib/html/doc/interface/Attr.dartdoc
deleted file mode 100644
index e212a0b81057c982aa8ccf3d2241e3c0dd4b1828..0000000000000000000000000000000000000000
--- a/lib/html/doc/interface/Attr.dartdoc
+++ /dev/null
@@ -1,26 +0,0 @@
-// 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 Attr
-interface Attr extends Node {
-
-  /** @domName Attr.isId */
-  final bool isId;
-
-  /** @domName Attr.name */
-  final String name;
-
-  /** @domName Attr.ownerElement */
-  final Element ownerElement;
-
-  /** @domName Attr.specified */
-  final bool specified;
-
-  /** @domName Attr.value */
-  String value;
-}