Add COU v2 docs

Author: aditya-67

api-references/payments/billpay.json

@@ -1508,8 +1508,7 @@
                             "QUARTERLY",
                             "HALFYEARLY",
                             "YEARLY",
-                            "ASPRESENTED",
-                            "NA"
+                            "ASPRESENTED"
                           ],
                           "type": "string",
                           "example": "ONETIME",