Fix number of parameters

Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/accounts/pipeline.py

@@ -79,7 +79,7 @@ def send_validation(strategy, backend, code):
     )
 
 
-def verify_open(backend, user, **kwargs):
+def verify_open(strategy, user=None, **kwargs):
     '''
     Checks whether it is possible to create new user.
     '''