[V2.0.4] Refund always send amount===0 to payment method createRefund function

[tianyingchun]

Describe the bug
Refund always send amount===0 to payment method createRefund function

To Reproduce
Steps to reproduce the behavior:

2. choose check box refund shipping (0.00)

3. in payment method

   createRefund: async (ctx, input, amount, order, payment, args) => {
        const transactionId = payment.transactionId;
        try {
....

we always received amount equal to zero

Expected behavior
should correct return refund amount

Environment (please complete the following information):

• @vendure/core version: 2.0.4
• Nodejs version 18
• Database (mysql/postgres etc):mysql

Additional context
Add any other context about the problem here.