Bug 27680: (QA follow-up) Update test for dbic_merge_sorting

Bug 27680: (QA follow-up) Update test for dbic_merge_sorting

The order_by handling will now always return an arrayref of ordering
hashrefs even when only one ordering hash is present. This is
interpreted by dbic as equivilent so I just update the test to pass
here.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 96aa6877ae39c987214e46d00c70c76591da0174)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>