Demos: There can be only one button.js

(cherry picked from commit b12cf01)

Author: jzaefferer

demos/dialog/modal-confirmation.html

@@ -11,7 +11,6 @@
 	<script src="../../ui/jquery.ui.button.js"></script>
 	<script src="../../ui/jquery.ui.draggable.js"></script>
 	<script src="../../ui/jquery.ui.position.js"></script>
-	<script src="../../ui/jquery.ui.button.js"></script>
 	<script src="../../ui/jquery.ui.dialog.js"></script>
 	<link rel="stylesheet" href="../demos.css">
 	<script>