Update uvicorn to 0.31.0

[pyup-bot]

This PR updates uvicorn[standard] from 0.30.6 to 0.31.0.

Changelog

0.31.0

Added

Improve `ProxyHeadersMiddleware` (2468) and (2231):

- Fix the host for requests from clients running on the proxy server itself.
- Fallback to host that was already set for empty x-forwarded-for headers.
- Also allow to specify IP Networks as trusted hosts. This greatly simplifies deployments
on docker swarm/kubernetes, where the reverse proxy might have a dynamic IP.
 - This includes support for IPv6 Address/Networks.

Links

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