Bug 29933: Fix stray usage of jquery.cookie.js plugin

Bug 29933: Fix stray usage of jquery.cookie.js plugin

This patch removes a few instances where the old cookie plugin was still
being used for deleting cookies even though the new plugin is being used
to set the cookies.

To test, apply the patch and test the following processes in the staff
interface:

Search to hold:

 - View a patron record and click the "Search to hold" button.
 - Perform a catalog search which will return results.
 - On the search results page there should be a "Place hold for
   <patron>" link under each holdable title.
 - Click the "Place hold" button's dropdown arrow and choose "Forget
   <patron>." The "Place hold for..." links should disappear.

Search to hold for a patron club:

 - If necessary, create a patron club.
 - Add one or more patrons to the club.
 - In Tools -> Patron clubs, find the club you added patrons to.
 - Click the "Actions" button and then "Search to hold."
 - Perform a catalog search which will return results.
 - On the search results page there should be a "Place hold for
   <club>" link under each holdable title.
 - Click the "Place hold" button's dropdown arrow and choose
   "Forget <club>." The "Place hold for..." links should disappear.

Batch item modification show/hide columns:

 - Go to Tools -> Batch item modification.
 - Submit a list of items for modification.
 - Uncheck some checkboxes to hide columns on the page showing the items
   you submitted.
 - In the browser's storage inspector (e.g.
   https://developer.mozilla.org/en-US/docs/Tools/Storage_Inspector),
   should see a "showColumns" cookie with a string of numbers and
   slashes.
 - Click the "Show all columns" checkbox.
 - The "showColumns" cookie should disappear.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>