Fix name of outbound opt-out to billing test and remove opt-out from billing to transport test (there is no separate logic for routing outbound opt-out messages after billing now so this test ended up looking like a duplicate of the non-opt-out version of the same test).
Fix name of outbound opt-out to billing test and remove opt-out from billing to transport test (there is no separate logic for routing outbound opt-out messages after billing now so this test ended up looking like a duplicate of the non-opt-out version of the same test).

praekelt/vumi-go,praekelt/vumi-go,praekelt/vumi-go,praekelt/vumi-go