Bug 14778: Remove t/Acquisition/Invoices.t

Bug 14778: Remove t/Acquisition/Invoices.t

Using Test::DBIx::Class now, we cannot do what we did in this file with DBD::Mock.
Since the Invoice[s] subroutines are already tested in
t/db_dependent/Acquisition/Invoices.t there is no special needs to have
these ones.
Instead of loosing 2 hours on this file, I would prefer to remove it.
Feel free to provide a counter patch.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>