[Sphere] Fix volume computation

include/hpp/fcl/shape/geometric_shapes.h

@@ -143,7 +143,7 @@ public:
 
   FCL_REAL computeVolume() const
   {
-    return 4 * boost::math::constants::pi<FCL_REAL>() * radius * radius / 3;
+    return 4 * boost::math::constants::pi<FCL_REAL>() * radius * radius * radius / 3;
   }
 };