Bump httpx from 0.21.1 to 0.23.0 in /graph-generator

Bumps [httpx](https://github.com/encode/httpx) from 0.21.1 to 0.23.0.
- [Release notes](https://github.com/encode/httpx/releases)
- [Changelog](https://github.com/encode/httpx/blob/master/CHANGELOG.md)
- [Commits](encode/httpx@0.21.1...0.23.0)

---
updated-dependencies:
- dependency-name: httpx
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]