Removed outdated comment.

src/karts/kart.cpp

@@ -1761,7 +1761,6 @@ void Kart::crashed(const Material *m, const Vec3 &normal)
         // a fence.
         btVector3 gravity = m_body->getGravity();
         gravity.normalize();
-        // Cast necessary since otherwise to operator- (vec3/btvector) exists
         Vec3 impulse =  normal - gravity* btDot(normal, gravity);
         if(impulse.getX() || impulse.getZ())
             impulse.normalize();