Updating the samples page to reflect the examples that have been retired.

src/site/samples/tracker/example/css/index.css

Index: src/site/samples/tracker/example/css/index.css
diff --git a/src/site/samples/tracker/example/css/index.css b/src/site/samples/tracker/example/css/index.css
deleted file mode 100644
index 767bde5f55ab57c4a1005290d8e4a8add50524f2..0000000000000000000000000000000000000000
--- a/src/site/samples/tracker/example/css/index.css
+++ /dev/null
@@ -1,18 +0,0 @@
-/*
-Copyright (c) 2013, 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.
-*/
-
-* {
-  margin: 0;
-  padding: 0;
-}
-
-ul {
-  list-style: none;
-}
-
-html {
-  overflow-y: scroll;
-}