Clean up translations

[TobiGr]

In #9092 @AudricV noticed new, but empty translations.I took a closer look at Weblate: We have
9 languages at 0% (0 of 721 translated) [ars, ay, ayc, dum, enm, ang, nds, ks, scn]
1 at 1% (1 of 721), [af]
1 at 1% (2 of 721), [kk]
1 at 1% (4 of 721), [si]
1 at 1% (13 of 721) [ace]
I suggest to remove those if no activity occurs until the next RC. This should be done by an admin on weblate,

Originally posted by @TobiGr in #9092 (comment)

---

Done in #9179:

While cleaning up the translations, we should also add the new localisations to our in-app language chooser, e.g. see #5721. New languages are e.g. Icelandic. This is an easy task which can be done by everybody and might be good to get used to the codebase a little. Help is appreciated.

[HotDryNoodle-WH]

Hi Tobi, can you assign this issue to me？ I'd be happy to add the new localisations to our in-app language chooser and I'll finish some unfinished translation work on weblate.