Bug 29501: Use the default transport

Bug 29501: Use the default transport

This patch makes the script pass the default SMTP transport to the
->send_or_die call.

The default is picked as this is the current behavior. New enhancements
could add the *library_id* to the message_queue table, and allow using
different transports depending on that. But it is out of the scope of
this bug.

To test:
1. Verify messages are being sent.
2. Sign off :-D

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
JD amended patch: revert
-        unless $format =~ m[^html$|^csv$|^ods$];
+        unless $format =~ m/^html$|^csv$|^ods$/;
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>