Bump .NET 8.0 (#5479)

BTCPayServer/Controllers/UIInvoiceController.UI.cs

@@ -550,6 +550,7 @@ namespace BTCPayServer.Controllers
                 Html = "Refund successfully created!<br />Share the link to this page with a customer.<br />The customer needs to enter their address and claim the refund.<br />Once a customer claims the refund, you will get a notification and would need to approve and initiate it from your Store > Payouts.",
                 Severity = StatusMessageModel.StatusSeverity.Success
             });
+
             ctx.Refunds.Add(new RefundData
             {
                 InvoiceDataId = invoice.Id,