Bump traitlets from 5.8.0 to 5.9.0 (#1946)

Bumps [traitlets](https://github.com/ipython/traitlets) from 5.8.0 to 5.9.0.
- [Release notes](https://github.com/ipython/traitlets/releases)
- [Changelog](https://github.com/ipython/traitlets/blob/main/CHANGELOG.md)
- [Commits](ipython/traitlets@v5.8.0...v5.9.0)

---
updated-dependencies:
- dependency-name: traitlets
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

setup.py

@@ -124,7 +124,7 @@ def package_files(prefix: str, directory: str, extension: str):
     'sphinx_panels==0.6.0',
     'sphinxcontrib-images==0.9.4',
     'pytest_codeblocks==0.16.1',
-    'traitlets==5.8.0',
+    'traitlets==5.9.0',
     'nbsphinx==0.8.12',
     'pandoc==2.3',
     'pypandoc==1.10',