Bug 23398: Disable the XML import/export format for biblio framework

Bug 23398: Disable the XML import/export format for biblio framework

It gives incomplete results and not sure it ever worked.
To prevent data loss it is better to remove this option.

Note that the code in C4/ImportExportFramework.pm is too complex to
attach with this patch to deletion of the code related to the XML
import/export. Safer to keep it for a separate bug report.

Test plan:
Import/export biblio frameworks and confirm that there is no more
reference to the xml format.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit ed45a4f333fb9f6569d150410ef99d8ffe13f54c)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>