Bug 30534: Remove guarantor_id attribute from the patron object

Bug 30534: Remove guarantor_id attribute from the patron object

This patch removes an attribute that was actually removed 3 years ago
and causes an exception when trying to search for it. The API responses
don't include it anyways.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
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>