Update Example_Interface_3.ts to reflect book text

[kurtishouser]

The supporting text for this example reads as follows: "In the preceding snippet, we build a product object and then pass it to our class's makeProduct function. We then console out the results, which is the same as before, except now our functional code is wrapped in a class."

So I'm assuming line 34 should be newProduct.makeProduct() instead of newProduct.product.

Note: I'm accessing the book online through O'Reilly. newProduct.product is present in the example code there as well.