Correctly use the specified units when calculating clusters

Previously we would use a hardcoded kilometers unit against maxDistance. Instead we specify options.units and use
the default kilometers distance arg when it was not specified. This carries forward the original intent of the PR
and fixes the bug where even after the revert of the kdbush change we were not honoring the units option when
creating clusters.

Author: mfedderly

packages/turf-clusters-dbscan/index.ts

@@ -142,7 +142,7 @@ function clustersDbscan(
         const neighborIndex = neighbor.index;
         const neighborPoint = points.features[neighborIndex];
         const distanceInKm = distance(point, neighborPoint, {
-          units: "kilometers",
+          units: options.units,
         });
         return distanceInKm <= maxDistance;
       }