Update create-quickstart.6.x.py

[agewang]

The code samples in this GitHub repository were automatically generated using a tool built at Twilio called Yoyodyne. The samples are updated when there is a change to the Twilio API or to the code generation tool.

However, contributions are still welcome! If you see something that doesn't look right, or a sample that seems to be missing, please do submit a PR. While we can't merge it directly in, it will help us improve the code samples for everyone.