Bug 22690: (QA follow-up) Silence manually generated warnings

Bug 22690: (QA follow-up) Silence manually generated warnings

In our test setup we mock the index_records() to produce warnings like
this:

Koha::Item at t/db_dependent/Koha/SearchEngine/Indexer.t line
93.

By wrapping all our item creations to warnings_are{} we can silence them.

Signed-off-by: Joonas Kylmälä <joonas.kylmala@helsinki.fi>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>