Removes use of #handle_asynchronously, which we need to do elsewhere. Fixes:
BulkInvoiceService#start_pdf_job starts a background process to create a pdf with multiple invoices
Failure/Error:
expect do
service.start_pdf_job [1, 2]
end.to enqueue_job Delayed::PerformableMethod
expected to enqueue exactly 1 jobs, but enqueued 0
# ./spec/services/bulk_invoice_service_spec.rb:8:in `block (3 levels) in <top (required)>'
