With Set Expiration Date, do not add time to the expiration date based on when marked success.

[kimwhite]

Describe the bug
When using a Set expiration date, for example, 2025-12-31, the user expiration date changes based on when the user pays. So if the payment is marked 3 days after checkout, the expiration gets set as 2026-01-02.

To Reproduce
Steps to reproduce the behavior:

1. Add Set Expiration Date to a set date
2. Checkout out Pay by Check
3. 3 days later, mark order successful
4. See incorrect expiration date