Don't allow refund to be higher than the order total

FYI it turned out that we had some custom code that was responsible for this, so the fix was in custom code rather than the main Commerce module.

We have a scenario involving upgrade and downgrade options. When a user upgrades to a higher plan, downgrades to a lower plan, and then cancels the purchase, it may result in a situation where we need to refund an amount greater than the current order value.

The patch below helps prevent this issue and ensures proper handling of such cases.