Bug 32734: (QA follow-up) Remove stray method

Bug 32734: (QA follow-up) Remove stray method

On bug 33083 we introduce a better way to implement a reusable method
for the same functionality.

This patch just removes the one in `Koha::Biblios` and the result should
be the same as the one inherited from  `Koha::Objects::Record::Collections` will be picked instead.

To test:
1. Run:
   $ prove t/db_dependent/Koha/Biblios.t \
           t/db_dependent/api/v1/biblios.t
=> SUCCESS: Tests pass!
2. Apply this patch
3. Repeat 1
=> SUCCESS: Tests pass!

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>