Update black requirement from <23.4 to <23.8

Updates the requirements on [black](https://github.com/psf/black) to permit the latest version.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/main/CHANGES.md)
- [Commits](psf/black@19.10b0...23.7.0)

---
updated-dependencies:
- dependency-name: black
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -8,5 +8,5 @@ mistune>=2.0.3,<2.1
 CacheControl[filecache]>= 0.11.7, < 0.14
 CacheControl[filecache]< 0.13;python_version<='3.6'
 urllib3<2;python_version<='3.6'
-black<23.4
+black<23.8
 mypy_extensions