Bump notebook from 6.4.1 to 6.4.2
Bump notebook from 6.4.1 to 6.4.2

Bumps [notebook](https://github.com/jupyter/jupyterhub) from 6.4.1 to 6.4.2.
- [Release notes](https://github.com/jupyter/jupyterhub/releases)
- [Changelog](https://github.com/jupyterhub/jupyterhub/blob/main/CHECKLIST-Release.md)
- [Commits](https://github.com/jupyter/jupyterhub/commits)

---
updated-dependencies:
- dependency-name: notebook
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
jhamrick/nbgrader,jupyter/nbgrader,jhamrick/nbgrader,jupyter/nbgrader,jupyter/nbgrader,jhamrick/nbgrader,jhamrick/nbgrader,jupyter/nbgrader,jupyter/nbgrader