API Updates

[anniel-stripe]

Codegen for openapi v249.
cc @stripe/api-libraries

Changelog

• Add support for cancellation_details on Subscription
• Fix return types on custom methods (extends stripe->customers->retrievePaymentMethod returns the wrong class (type hint) #1446)

[richardm-stripe]

Looks like there's some fixed docstrings too? Worth mentioning in the changelog. There was probably a generator fix for custom method return types.