Fix REST API version calculation

netbox/netbox/settings.py

@@ -455,7 +455,7 @@ FILTERS_NULL_CHOICE_VALUE = 'null'
 # Django REST framework (API)
 #
 
-REST_FRAMEWORK_VERSION = VERSION[0:3]  # Use major.minor as API version
+REST_FRAMEWORK_VERSION = VERSION.rsplit('.', 1)[0]  # Use major.minor as API version
 REST_FRAMEWORK = {
     'ALLOWED_VERSIONS': [REST_FRAMEWORK_VERSION],
     'DEFAULT_AUTHENTICATION_CLASSES': (