Update pynacl to 1.6.0

[pyup-bot]

This PR updates pynacl from 1.5.0 to 1.6.0.

Changelog

1.6.0

------------------
* **BACKWARDS INCOMPATIBLE:** Removed support for Python 3.6 and 3.7.
* Added support for the low level AEAD AES bindings.
* Added support for ``crypto_core_ed25519_from_uniform``.
* Update ``libsodium`` to 1.0.20-stable (2025-08-27 build).
* Added support for free-threaded Python 3.14.
* Added support for Windows on ARM wheels.

Links

• PyPI: https://pypi.org/project/pynacl
• Changelog: https://data.safetycli.com/changelogs/pynacl/
• Repo: https://github.com/pyca/pynacl/