Bug 29537: Remove unnecessary if-else checks for soonest renew date

Bug 29537: Remove unnecessary if-else checks for soonest renew date

GetSoonestRenewDate() calculates the renewal due date now also
correctly for auto-renewals after the fixes from bug 29476 so we don't
have to add any if-else checks because of it being buggy anymore.

To test:
 1) prove t/db_dependent/Circulation.t

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>