Update Haversine.java

Comentario arreglado ortográficamente.

Author: HsJm03

src/main/java/com/thealgorithms/geometry/Haversine.java

@@ -13,7 +13,7 @@
  */
 public final class Haversine {
 
-    // Average radius of Earth in kilometers
+    // Average radius of Earth in kilometers.
     private static final double EARTH_RADIUS_KM = 6371.0;
 
     /**