Remove generated directories with 100s of files.

client/html/generated/html/frog/_XMLSerializerFactoryProvider.dart

Index: client/html/generated/html/frog/_XMLSerializerFactoryProvider.dart
diff --git a/client/html/generated/html/frog/_XMLSerializerFactoryProvider.dart b/client/html/generated/html/frog/_XMLSerializerFactoryProvider.dart
deleted file mode 100644
index e71f841df42d5fba3ef642eef71c7a5fd21879af..0000000000000000000000000000000000000000
--- a/client/html/generated/html/frog/_XMLSerializerFactoryProvider.dart
+++ /dev/null
@@ -1,8 +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.
-
-class _XMLSerializerFactoryProvider {
-  factory XMLSerializer() native
-      '''return new XMLSerializer();''';
-}