Avoid stack level too deep on api/payments_controller_spec

Reapply changes from 74088fb040fe72649613d448cdb1bcb355339ad0 missed
that in one of the last merges
Remove deleted_at scope from `variants_including_master`

paranoia gem already takes care of that
Fix api/orders_controller_spec

Stub `permitted_line_item_attributes` so that controller recognizes
extra parameter included on the spec