Bug 19163: Critical typo in stage-marc-import process

Bug 19163: Critical typo in stage-marc-import process

Template says ISO2709 but script wants MARC or MARCXML..
Slipped in with bug 19049.
Trivial but critical fix.

Test plan:
Import a MARC file.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
I picked this fix because I think MARC is always ambiguous. ISO2709
clearly denotes the serialization format used.

Signed-off-by: Liz Rea <liz@catalyst.net.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit af791d83e435587494fa04a45375f48a3e2ad236)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>