fix sorting enum for trxChargeDate

Author: dalilaacqua

src/idpay/apim/api/idpay_merchants_portal/openapi.merchants.portal.yml

@@ -1036,6 +1036,9 @@ paths:
           description: "Sorting criteria in the format: property,(asc|desc). Default: elaborationDateTime,desc"
           schema:
             type: string
+            enum:
+              - trxChargeDate, desc
+              - trxChargeDate, asc
         - name: fiscalCode
           in: query
           description: Fiscal Code