How to remove Project Invoice Approval Validation

We are implementing Projects Contract Billing and we have setup the Invoice Approval Workflow as serial: approving first Project Team Member A and then Project Team Member B

When we have multiple invoices for the same contract and we submit them for approval Project Team Member A approves the first invoice and when goes to approve the second invoice the system displays the following Error message:

You can't approve this invoice because the contract contains preceding invoices that are unapproved PJB-2190079. You must approve invoices in the order they were created. Approve the existing invoices for this contract in numeric order before approving this invoice