l10n: fr.po remove obsolete entries

On NetBSD, the version of msgfmt is still 0.14.4. There's no hope for
an upgrade due to some GPLv3 allergy of NetBSD's. This version chokes
on heavily decorated commented entries in po files. It's safer to get
rid of all these obsolete entries.
Signed-off-by: NJean-Noël Avila <jn.avila@free.fr>