Bump notebook from 7.2.2 to 7.5.6 in /docs

Bumps [notebook](https://github.com/jupyter/notebook) from 7.2.2 to 7.5.6.
- [Release notes](https://github.com/jupyter/notebook/releases)
- [Changelog](https://github.com/jupyter/notebook/blob/@jupyter-notebook/tree@7.5.6/CHANGELOG.md)
- [Commits](https://github.com/jupyter/notebook/compare/@jupyter-notebook/tree@7.2.2...@jupyter-notebook/tree@7.5.6)

---
updated-dependencies:
- dependency-name: notebook
  dependency-version: 7.5.6
  dependency-type: direct:production
...

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

Author: dependabot[bot]

docs/notebook_requirements.txt

@@ -29,7 +29,7 @@ nbclient==0.10.0
 nbconvert==7.17.0
 nbformat==5.10.4
 nest-asyncio==1.6.0
-notebook==7.2.2
+notebook==7.5.6
 numexpr==2.10.1
 pandocfilters==1.5.1
 parso==0.8.4