devel/libkiwix: Revert update to 14.0.0 (so, → 13.1.0)

The latest release of www/kiwix-tools, which is still 3.7.0, does not
work with libkiwix 14.0.0, so the update was premature.

We will be able to update libkiwix only when the new release of
www/kiwix-tools is out. (The alternative of maintaining a few libkiwix
ports with different versions does not seem worth it.)

This is a maintainer update (olce.freebsd.ports@certner.fr).

This reverts commit dafb538b3fd6 (devel/libkiwix: Update to 14.0.0, 2024-12-26).

Fixes: dafb538b3fd6 ("devel/libkiwix: Update to 14.0.0")