[ast, es, fr, nn] Update byte unit translations

[ast, es, fr, nn] Update byte unit translations

The Asturian, French, Norwegian Nynorsk and Spanish translations
incorrectly translated "MB" and friends to "MiB" (french: "Mio"), etc.

This was in response to the incorrect use of "MB" in the (now
deprecated) g_format_size_for_display() function.

These strings are now used (correctly) in g_format_size(), so I have
updated the translations accordingly.

Additionally, the Norwegian Nynorsk translation was incorrectly
translating several larger units to "KiB", so that has been corrected as
well.