Bug 35787: Remove Koha::Template::Plugin::Biblio::CanBook

Bug 35787: Remove Koha::Template::Plugin::Biblio::CanBook

We can replace it with biblio.items.filter_by_bookable, no need to have this TT method.

Additionally there was no test for it.

Test plan:
Make sure the Bookings tab on the left of the biblio detail page is
displayed when needed.

Note that there is also a "Place booking" button that should appear in
the toolbar.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>