build(deps): update papermill requirement in /docker/py (#445)

Updates the requirements on [papermill](https://github.com/nteract/papermill) to permit the latest version.
- [Changelog](https://github.com/nteract/papermill/blob/main/docs/changelog.md)
- [Commits](nteract/papermill@2.5.0...2.6.0)

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

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

docker/py/requirements.txt

@@ -5,7 +5,7 @@ jupyter-server-proxy==4.1.2
 jupyterlab-git==0.50.0
 jupyterlab-system-monitor~=0.8.0
 mistune>=2.0.1 # not directly required, pinned by Snyk to avoid a vulnerability
-papermill~=2.5.0
+papermill~=2.6.0
 requests>=2.20.0
 setuptools>=65.5.1 # not directly required, pinned by Snyk to avoid a vulnerability
 virtualenv>=20.7.2