Bug 34872: Add page-section to cart pop-up in staff interface

Bug 34872: Add page-section to cart pop-up in staff interface

This adds the page-section class to the tables in the cart pop-up
in the staff interface.

To test:
* Search for records in the staff interface and add some to the cart
* Open the cart, review the normal and brief view
* Apply patch
* Review normal and brief view again - tables/sections should now
  have the white background.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit 34749a20bddccfa853e3abf8bae104c07bb89db5)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>