Update whitenoise to 6.12.0

[pyup-bot]

This PR updates whitenoise from 6.11.0 to 6.12.0.

Changelog

6.12.0

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

* Drop Python 3.9 support.
* Fix potential unauthorised file access vulnerability in "autorefesh" mode. See `PR 684 <https://github.com/evansd/whitenoise/pull/684>`__ for details, and a reminder that autorefresh mode has always been documented as unsuitable for production use. Thanks Seth Larson for reporting.

Links

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