Bug 31793: (QA follow-up) DelAuthority doesn't return errors

Bug 31793: (QA follow-up) DelAuthority doesn't return errors

DelAuthority doesn't return an error, so the only possible error
conditions are exceptions, that are unknown for now. Removing the error
checking control structure and the 409 error returning, which is
inherited from DelBiblio's call on the biblios endpoint.

It will now just return a 500 in the event of an unhandled internal
error.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>