Bump nbconvert from 7.2.2 to 7.8.0

Bumps [nbconvert](https://github.com/jupyter/nbconvert) from 7.2.2 to 7.8.0.
- [Release notes](https://github.com/jupyter/nbconvert/releases)
- [Changelog](https://github.com/jupyter/nbconvert/blob/main/CHANGELOG.md)
- [Commits](jupyter/nbconvert@v7.2.2...v7.8.0)

---
updated-dependencies:
- dependency-name: nbconvert
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

docs/requirements_docs.txt

@@ -45,7 +45,7 @@ mistune==2.0.4
 myst_parser==0.18.1
 natsort==8.2.0 
 nbclient==0.7.0 
-nbconvert==7.2.2 
+nbconvert==7.8.0 
 nbformat==5.7.0 
 nbsphinx==0.8.9 
 nest-asyncio==1.5.6