Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/BRElement.dartdoc

Index: lib/html/doc/interface/BRElement.dartdoc
diff --git a/lib/html/doc/interface/BRElement.dartdoc b/lib/html/doc/interface/BRElement.dartdoc
deleted file mode 100644
index 9f9ad21ed3539ab539b26d060a2aa01f63b166b5..0000000000000000000000000000000000000000
--- a/lib/html/doc/interface/BRElement.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 HTMLBRElement
-interface BRElement extends Element default _Elements {
-
-  BRElement();
-
-  /** @domName HTMLBRElement.clear */
-  String clear;
-}