Browser blocks admin page resources on HTTPS sites

When visiting the plugin’s admin page, Google Chrome shows this in the console:

Mixed Content: The page at ‘https://www.ronitbaras.com/wp-admin/options-general.php?page=democracy-poll&subpage=l10n’ was loaded over HTTPS, but requested an insecure stylesheet ‘http://ajax.googleapis.com/ajax/libs/jqueryui/1.11.2/themes/smoothness/jquery-ui.css?ver=4.5.3’. This request has been blocked; the content must be served over HTTPS.

Line 72 in class.DemAdmininit.php should be changed to:

wp_enqueue_style('jquery-style', '//ajax.googleapis.com/ajax/libs/jqueryui/1.11.2/themes/smoothness/jquery-ui.css');

https://ww.wp.xz.cn/plugins/democracy-poll/