Bug 36875: (follow-up) Modify query in translated_content

Bug 36875: (follow-up) Modify query in translated_content

This removes the MySQLism for FIELD(..).
In this case we just want to get the non-default records in
the front. So we can just test lang=default. And prevent inserting
$lang in the expression. And so prevent execution in ORDER BY.
No longer needing the ->quote call too.

Test plan:
Run Koha/AdditionalContents.t again.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>