auth: fix docstring

Fixed small docstring mismatch

Author: marcinkuzminski

src/onelogin/saml2/auth.py

@@ -42,8 +42,8 @@ def __init__(self, request_data, old_settings=None, custom_base_path=None):
         :param request_data: Request Data
         :type request_data: dict
 
-        :param settings: Optional. SAML Toolkit Settings
-        :type settings: dict
+        :param old_settings: Optional. SAML Toolkit Settings
+        :type old_settings: dict
 
         :param custom_base_path: Optional. Path where are stored the settings file and the cert folder
         :type custom_base_path: string