[example][cleanup] Use geometry.jacobian(...) directly
Simplify examples by replacing the chain rule hack
gradient = referenceGradient * transpose(jacobianTransposed);
by plain use of
gradient = referenceGradient * jacobian;
Simplify examples by replacing the chain rule hack
gradient = referenceGradient * transpose(jacobianTransposed);
by plain use of
gradient = referenceGradient * jacobian;