For instance, in the target configuration, in Designer, you can open the Interface text edit settings tool (Edit > Edit interface text), use it to search for all localization items, then, in the search results, locate the items that are related to the unnecessary language and delete the items.
Please not that EDT can not show a lot of a languages. At least in my instance it had struggled with displaying 20 languages for intl version of Small business, some of languages were out of the screen space with no scroll.