revert: chore: upgrade jQuery UI to version 1.14.1 (openedx#37025) (openedx#37449)

This reverts commit e427078.

Author: bradenmacdonald

common/static/js/vendor/jquery-ui.min.js

@@ -24,7 +24,7 @@
     $.ajaxWithPrefix = $.ajax;
   </script>
   <!-- The Video XBlock requires "Slider" from jQuery-UI: -->
-  <script src="https://code.jquery.com/ui/1.14.1/jquery-ui.min.js"></script>
+  <script src="https://code.jquery.com/ui/1.12.1/jquery-ui.min.js"></script>
   <!-- The video XBlock depends on Underscore.JS -->
   <script type="text/javascript" src="{{ lms_root_url }}/static/common/js/vendor/underscore.js"></script>
   <!-- The video XBlock depends on jquery-cookie -->