Hint on documentation of function get_product()

The hint actual says that return void, changed to WC_Product_Simple because $woocommerce->product_factory->get_product() returns WC_Product_Simple, this change is useful for IDEs autocomplete hints
Update proposal hint on documentation of function get_product()
Update proposal hint on documentation of function get_product()

Update proposal hint on documentation of function `WC_Product_Factory::get_product()` from `void` to an generic `WC_Product`
Merge pull request #3411 from jprieton/patch-1

Hint on documentation of function get_product()