Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/DetailsElement.dartdoc

Index: lib/html/doc/interface/DetailsElement.dartdoc
diff --git a/lib/html/doc/interface/DetailsElement.dartdoc b/lib/html/doc/interface/DetailsElement.dartdoc
deleted file mode 100644
index 27bc5f2dab0c6c559ca8a3b06c0f589042154d71..0000000000000000000000000000000000000000
--- a/lib/html/doc/interface/DetailsElement.dartdoc
+++ /dev/null
@@ -1,16 +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 HTMLDetailsElement
-interface DetailsElement extends Element default _Elements {
-
-  DetailsElement();
-
-  /** @domName HTMLDetailsElement.open */
-  bool open;
-}