Update pydantic to 2.6.4

[pyup-bot]

This PR updates pydantic from 2.6.3 to 2.6.4.

Changelog

2.6.4

[GitHub release](https://github.com/pydantic/pydantic/releases/tag/v2.6.4)

What's Changed

Fixes

* Fix usage of `AliasGenerator` with `computed_field` decorator by sydney-runkle in [8806](https://github.com/pydantic/pydantic/pull/8806)
* Fix nested discriminated union schema gen, pt 2 by sydney-runkle in [8932](https://github.com/pydantic/pydantic/pull/8932)
* Fix bug with no_strict_optional=True caused by API deferral by dmontagu in [8826](https://github.com/pydantic/pydantic/pull/8826)

Links

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