refactor(phpstand): update coupon code and physical coupon product

This commit modifies the `src/QUI/ERP/Coupons/CouponCode.php` by removing an unexplained variable
annotation.
In `src/QUI/ERP/Coupons/Products/PhysicalCouponProductType.php`, it introduces an import statement
for `QUI\\Locale` and updated the `Locale` parameter type definition in `getTypeDescription`
function. This change improves code readability and consistency.