Bump black from 24.8.0 to 26.3.1 in /packages/typespec-python

Bumps [black](https://github.com/psf/black) from 24.8.0 to 26.3.1.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/main/CHANGES.md)
- [Commits](psf/black@24.8.0...26.3.1)

---
updated-dependencies:
- dependency-name: black
  dependency-version: 26.3.1
  dependency-type: direct:development
...

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

Author: dependabot[bot]

packages/typespec-python/dev_requirements.txt

@@ -7,7 +7,7 @@ colorama==0.4.6
 debugpy==1.8.12
 pytest==8.3.4
 coverage==7.6.1
-black==24.8.0
+black==26.3.1
 ptvsd==4.3.2
 types-PyYAML==6.0.12.20241230