Bug 23177: (QA follow-up) Remove subtest txn_begin and rollback

Bug 23177: (QA follow-up) Remove subtest txn_begin and rollback

This resolves:
DBIx::Class::Storage::txn_rollback(): A txn_rollback in nested transaction is ineffective! (depth 1)
Removing unneeded subtest txn's. We should probably add them everywhere or
just at global level.

Test plan:
With all three patches applied, run Circulation.t a few times.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit c7a707d60b187fa2c18c4bacd3a6b472de25da98)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>