Bug 34181: Fix jQuery selector to make delete checkboxes reappear

Bug 34181: Fix jQuery selector to make delete checkboxes reappear

Bug 32257 changed the page structure slightly to fix a display
issue with the labels. This resulted in a broken selector in the
function for displaying the checkboxes for deleting/emptying a
certain patron field.

To test:
* Go to Tools > Batch patron modifications
* Enter some cardnumbers or borrowernumbers
* On the batch patron edit form, verify that the checkboxes
  behind each input field are missing
* Apply patch
* Verify the checkboxes reappeared
  * Verify that for mandatory fields the checkbox is locked
* Make some batch edits and verify the checkboxes work as
  intended

Signed-off-by: Lisette Scheer <lisette.scheer@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>