Bug 33568: Prevent api/v1/biblios.t to fail randomly

Bug 33568: Prevent api/v1/biblios.t to fail randomly

koha_1       |     #   Failed test 'The items are returned'
koha_1       |     #   at t/db_dependent/api/v1/biblios.t line 196.
koha_1       |     #     Structures begin differing at:
koha_1       |     #          $got->[0]{external_id} = 'th151O2JtgfGdVW6aiF'
koha_1       |     #     $expected->[0]{external_id} = 'uxrMzUXrkHQy7MHOSfjK'
koha_1       |     # Looks like you failed 1 test of 11.
koha_1       |
koha_1       | #   Failed test 'get_items() tests'
koha_1       | #   at t/db_dependent/api/v1/biblios.t line 206.

Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>