Bug 19013: Fix borrowers.guarantorid in sammple_patrons.sql

Bug 19013: Fix borrowers.guarantorid in sammple_patrons.sql

That breaks randomly tests on Jenkins (Koha/Patrons.t)

It certainly affects data in other languages but I did not find a quick
and easy way to modify this file (replace all guarantorid values with
NULL)

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

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit b7d291a1ee692d6de71503683a3e61c9311c33d8)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>