Change wiki preprocessing script to read redirect pages

Change wiki preprocessing script to read redirect pages

The script that preprocess keys and tags metadata from the wiki
was filtering redirect pages when looking for wiki pages with the
template `KeyDescription`.

Some wiki pages like `Key:admin_level` currently redirects to others
like `Tag:boundary=administrative`, but even so, they still contain
a `KeyDescription` template so their metadata can be read by other
programs.

The parameter `eifilterredir` was changed and tested. For more
details, see this parameter in the feature `list=embeddedin` from
https://www.mediawiki.org/w/api.php.