[TASK] Fix weblate warning regarding ku lang.

Original warning:
> Files for translated languages are using ambiguous language codes.
> These language codes indicate a macrolanguage, and it is usually better to use the code of the individual language instead.

> Language code: ku
> Suggested individual language codes: ckb, kmr, sdh

I will arbitrally choose ckb because I ignore differences about those individual languages and I'am sorry for this.
Feel free to edit, open an issue or edit those individual languages.

Signed-off-by: Jerome Jutteau <jerome@jutteau.fr>

diff --git a/lib/locales/ku.json b/lib/locales/ckb.json
similarity index 100%
rename from lib/locales/ku.json
rename to lib/locales/ckb.json