Update French localization (#4437)
* Update French localization
* use `point m茅dian`
* Update messages.po
* add three new strings
* translate new string
* Apply suggestions from code review
Co-authored-by: Stanislas Signoud <signez@stanisoft.net>
* update revision date
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Co-authored-by: Stanislas Signoud <signez@stanisoft.net>
authored by