[Flask-Cors] Update type annotation for origins to also allow Pattern

[wvanbergen]

Small fix: this updates the type annotation for the origins argument for CORS() and CORS.init_app to also accept Patterns. Also, use Iterable rather than list to not cause compatibility issues.

• This reflects the typing of the origins argument of the cross_origin decorator.
• This matches the documentation: https://corydolphin.github.io/flask-cors/extension/
• This reflects what we have been running in production for many years.

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉