Remove API_VERSION

Author: AlexandrosMor

Adyen/settings.py

@@ -1,3 +1,4 @@
+# Those constants are used from the library only
 BASE_PAL_URL = "https://pal-{}.adyen.com/pal/servlet"
 BASE_HPP_URL = "https://{}.adyen.com/hpp"
 ENDPOINT_CHECKOUT_TEST = "https://checkout-test.adyen.com"
@@ -8,6 +9,3 @@
 API_RECURRING_VERSION = "v25"
 API_PAYMENT_VERSION = "v30"
 API_PAYOUT_VERSION = "v30"
-
-# Deprecated
-API_VERSION = "v30"