Update en.json to use traffic circle for all circles
Update en.json to use traffic circle for all circles

I haven't updated the 'roundabout exit' instructions here as I'm not sure 'traffic circle' is the best option in this case.

While 'rotary' and 'roundabout' are more precise, 'traffic circle' is more largely understood, at least in US English.
Project-OSRM/osrm-text-instructions,yuryleb/osrm-text-instructions