Bump nbsphinx from 0.8.8 to 0.8.9 (#1250)

Bumps [nbsphinx](https://github.com/spatialaudio/nbsphinx) from 0.8.8 to 0.8.9.
- [Release notes](https://github.com/spatialaudio/nbsphinx/releases)
- [Changelog](https://github.com/spatialaudio/nbsphinx/blob/master/NEWS.rst)
- [Commits](spatialaudio/nbsphinx@0.8.8...0.8.9)

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

Signed-off-by: dependabot[bot] <[email protected]>

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

Author: dependabot[bot]

requirements_docs.txt

@@ -14,5 +14,5 @@ sphinx-gallery==0.10.1
 sphinx-autodoc-typehints==1.18.1
 ansys-sphinx-theme==0.4.0
 pypandoc==1.8.1
-nbsphinx==0.8.8
+nbsphinx==0.8.9
 ipywidgets==7.7.0