Add back ar, my and ro to localization list

In commit 39ca163c I suspected that
too many locales were removed, and indeed it even caused stable to
FTBFS:

    Localize each supported browser locale
    The following supported browser locales lack descriptions in /usr/share/tails/browser-localization/descriptions: ar my ro
    E: config/chroot_local-hooks/11-localize_browser failed (exit non-zero). You should check for errors.

So I am re-adding at least those locales.