Toki Pona is a constructed language without a standard language code. There used to be a Wikipedia in it, so MediaWiki supports localization into by having a json localization file in core and some extensions. However, the Wikipedia is closed (and moved to Wikia), and translatewiki doesn't support localization into it.
Since the code is non-standard and wider activity is not expected, the code and the json files should be removed. It would be nice to give the maintainers of the Wikia site a way to keep the localization, however.
Copying/adapting the (incomplete?) to-do list from merged task (T178730#3701525):
 Toki Pona localization files be removed from MediaWiki,
 the ability to add descriptions in Toki Pona be removed from Wikidata,
 remove localizations from Translatewiki
 Update the [[https://translatewiki.net/wiki/Portal:Tokipona |Tokipona portal]] to reflect this new status