I don't think this is good.
@sylius what is the aim of this method? This is triggered on `finalize.pre_complete`. Update the payment amount if order has been modified between PaymentStep and FinalizeStep? If so we need to find another way to enforce payment details are good at FinalizeStep.
Because if we want to have multiple payments, then set the order total as amount of each payment is obviously not correct.
We cannot decide ourselves what to do if payments sum amount is different from order total. I think this should be dealt as error and not silently modified.