Fix fi_FI date formats
Leave the ISO date format "%Y-%m-%d" alone.
The long date format is printed with month format string "%OBta". This
uses the 'standalone' month name (because musl only supports that)
combined with the '-ta' suffix which results in correct month declension
for all the month names. With this format both strftime(..., "%c", tm)
in musl and g_date_time_format(dt, "%c")
in GLib print the date
and time in the correct format
Short dates use "." as separator (really an ordinal marker for days and months).