jquery-ui css should have low priority over phpmyadmin.css.php

phpmyadmin.css.php should be after jquery-ui-1.9.2.custom.css so that we can override properties of jquery-ui-1.9.2.custom.css in phpmyadmin.css.php as per our theme.

Signed-off-by: Chirayu Chiripal <chirayu.chiripal@gmail.com>