Bug 21848: Resolve unac_string warning from Circulation.t

Bug 21848: Resolve unac_string warning from Circulation.t

Just add "use utf8".

Test plan:
Run Circulation.t; verify there are no warnings.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit 3e731ce09433cf2121332f5356b27f90ccb34654)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit 4dbb5e636093c9145dc3f3d02de4b119d93b13fb)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>