[FIX] Voucher still assigns bank statement period instead of statement line period

In 6.1, we could not call super on create_move_from_st_line. In 7.0 it looked like we did because of refactorings driven by the good people of C2C but as it turns out, account_voucher's override of this method still insists in writing the statement period to the voucher that account_banking creates for each reconciled bank statement line. I see no other way than monkeypatching this out of account_voucher but I am taking care not to mess up other databases on the same instance.

Setting this file to noqa to preserve original style for easy detection of any upstream changes.