Download: Update download.jqueryui.com (drop support for <1.12)

Drop support fro jQuery UI older than `1.12` in the Download Builder
as previously announced.

Ref https://blog.jqueryui.com/2024/04/plans-for-jquery-ui-1-14-dropping-support-for-ui-1-12-in-the-download-builder/

Author: mgol