Bump the pip group across 1 directory with 2 updates

Bumps the pip group with 2 updates in the /packages/typespec-python directory: [pytest](https://github.com/pytest-dev/pytest) and [black](https://github.com/psf/black).


Updates `pytest` from 8.3.4 to 9.0.3
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/main/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@8.3.4...9.0.3)

Updates `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: pytest
  dependency-version: 9.0.3
  dependency-type: direct:development
  dependency-group: pip
- dependency-name: black
  dependency-version: 26.3.1
  dependency-type: direct:development
  dependency-group: pip
...

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

Author: dependabot[bot]

packages/typespec-python/dev_requirements.txt

@@ -6,9 +6,9 @@ tox-uv
 mypy==1.13.0
 colorama==0.4.6
 debugpy==1.8.12
-pytest==8.3.4
+pytest==9.0.3
 coverage==7.6.1
-black==24.8.0
+black==26.3.1
 ptvsd==4.3.2
 types-PyYAML==6.0.12.20241230