Comment 1 for bug 1681930

While looking into this, I found that xact_paid_total also had the incorrect type of int for unvoided amount, and corrected it as well.

working branch can be found here: https://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/gsams/LP1681930_xact_billing_totals_incorrect_column_type