Spinner tests: Remove mousewheel plugin

The plugin isn't needed nor used in the unit tests, which just trigger the
appropriate events. This works around the failure in Firefox 27/28 that we'll
try to track down separately.

Ref #9988

Author: jzaefferer

tests/unit/spinner/spinner.html

@@ -5,7 +5,6 @@
 	<title>jQuery UI Spinner Test Suite</title>
 
 	<script src="../../jquery.js"></script>
-	<script src="../../../external/jquery.mousewheel.js"></script>
 	<script src="../../../external/globalize.js"></script>
 	<script src="../../../external/globalize.culture.ja-JP.js"></script>
 	<link rel="stylesheet" href="../../../external/qunit.css">