[REF] Very minor simplification

[REF] Very minor simplification

ContributionParams is mostly passed in to processContribution
but a few parametrs are added to it within that function

This adds 2 of them to the passed in values for a very minor simplification.

Note that params['total_amount'] was set using order->getTotalAmount
and this will return a consistent result from anywhere in the postProcess
function (after line 1002)