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 the [MediaWiki API](https://www.mediawiki.org/w/api.php).