Update flask to 3.0.0

[pyup-bot]

This PR updates flask from 2.3.3 to 3.0.0.

Changelog

3.0.0

-------------

Released 2023-09-30

-   Remove previously deprecated code. :pr:`5223`
-   Deprecate the ``__version__`` attribute. Use feature detection, or
 ``importlib.metadata.version("flask")``, instead. :issue:`5230`
-   Restructure the code such that the Flask (app) and Blueprint
 classes have Sans-IO bases. :pr:`5127`
-   Allow self as an argument to url_for. :pr:`5264`
-   Require Werkzeug >= 3.0.0.

Links

• PyPI: https://pypi.org/project/flask
• Changelog: https://data.safetycli.com/changelogs/flask/

[pyup-bot]

Closing this in favor of #320