fix(directions): show a 9.96 km route as 10 km, not 10.0 km

routeDistanceText picked one decimal while the raw kilometres were under
10, then rounded them for display, so 9.95 km or more read "10.0 km".
It now picks the unit from the rounded tenth, as it already does at the
metre/kilometre boundary.

src/layers/directions/index.js

@@ -115,7 +115,8 @@ export function routeDistanceText(meters) {
   const tens = Math.round(meters / 10) * 10;
   if (tens < 1000) return formatQuantity(tens, 'm');
   const km = meters / 1000;
-  return km < 10
+  // Pick the unit from the tenth it prints: 9.96 km read "10.0 km".
+  return Math.round(meters / 100) < 100
     ? formatQuantity(km, 'km', {
         minimumFractionDigits: 1,
         maximumFractionDigits: 1,