Bug 30497: Recreate old_reserves_ibfk_4 when it cascades

Bug 30497: Recreate old_reserves_ibfk_4 when it cascades

Test plan:
Drop old_reserves_ibfk_4.
Add back with:
    alter table old_reserves ADD CONSTRAINT `old_reserves_ibfk_4` FOREIGN KEY (`itemtype`) REFERENCES `itemtypes` (`itemtype`) ON DELETE CASCADE ON UPDATE CASCADE;
Run dbrev. Check that constraint has been replaced by SET NULL.
Run dbrev again. No changes.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
[EDIT 23-08-22 Replaced DROP CONSTRAINT]

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>