Release testing instructions for WC Payments 5.6.0

Ensure WCPay JS loaded on Checkout page for zero order totals PR #5423

Testing steps

Test 1:

1. Add an item to cart.
2. Create a 100% discount coupon and add it to the cart, make sure cart total is 0
3. Navigate to checkout page, and remove the coupon.
4. Without refreshing the page, add a payment method and place the order

Test 2: Test that it works for all types of checkout (UPE, non-UPE, Blocks, Pay for Order etc) and other pages with Credit Card form. Test that there are no regression on normal checkout.