Fixed simple syntax error and copy/paste error in the python example.
Fixed simple syntax error and copy/paste error in the python example.

amzn/pay-with-amazon-express-demo,amzn/pay-with-amazon-express-demo,amzn/pay-with-amazon-express-demo,amzn/pay-with-amazon-express-demo,amzn/pay-with-amazon-express-demo,amzn/pay-with-amazon-express-demo,amzn/pay-with-amazon-express-demo