Issue #6406 Fix parameter mismatch

Signed-off-by: Syam G Krishnan <syamgk01@gmail.com>

synapse/handlers/register.py

@@ -266,7 +266,7 @@ class RegistrationHandler(BaseHandler):
             }
 
             # Bind email to new account
-            yield self._register_email_threepid(user_id, threepid_dict, None, False)
+            yield self._register_email_threepid(user_id, threepid_dict, None)
 
         return user_id