The Slovak translation was based on a slightly older en catalog, so the
translation parity test currently fails on main.
sk was missing ten keys that landed around the same time: the composer
attachment-upload validation strings, the recipient autocomplete
strings (translated to Slovak here) and the settings date_locale block
(kept as the same English values every other locale currently has).
The other twenty locales were missing language.sk in return - added as
the endonym "Slovenčina" (matching how the other entries are written),
and as "Slovacă" in ro, which translates its language names.
