Correct checkout url payments result

Author: AlexandrosMor

Adyen/client.py

@@ -141,7 +141,7 @@ def _determine_checkout_url(self, platform, service, action):
         if action == "paymentsDetails":
             action = "payments/details"
         if action == "paymentsResult":
-            action = "payment/result"
+            action = "payments/result"
         if action == "originKeys":
             api_version = settings.API_CHECKOUT_UTILITY_VERSION