update simplecookie usage

Author: idbentley

src/clerk_backend_api/jwks_helpers/authenticaterequest.py

@@ -93,9 +93,10 @@ def get_session_token(request: Requestish) -> Optional[str]:
         cookie_header = request.headers.get('cookie')
         if cookie_header is not None:
             if cookie_header is not None:
-                for key, value in SimpleCookie(cookie_header).items():
+                cookies = SimpleCookie(cookie_header)
+                for key in cookies.keys():
                     if key.startswith("__session"):
-                        return value
+                        return cookies[key].value
 
         return None