Update fr.json

[operon]

In french the roundabout is an "giratoire".
"Giratoire" is circular road with priority to vehicles that turn in circles. junction:roundabout https://osm.org/go/0BM0ndP58-- "Rond-point is a circular road with priority to vehicles entering in circles. junctionj:circular https://osm.org/go/0BPIBp61A--

[yuryleb]

Thanks, but it's better to update translation on https://www.transifex.com/project-osrm/osrm-text-instructions/ first and upload your changes here after (there is some script to do this).

[jcoupey]

There is indeed a subtle semantic distinction in french related to priorities as you clearly stated. On the other hand I wonder if it is really worth making a distinction here since it seems to me that most people use both terms as synonyms, and "rond-point" is much more common?

[1ec5]

Superseded by #312.