Bump nbsphinx from 0.9.2 to 0.9.3

Bumps [nbsphinx](https://github.com/spatialaudio/nbsphinx) from 0.9.2 to 0.9.3.
- [Release notes](https://github.com/spatialaudio/nbsphinx/releases)
- [Changelog](https://github.com/spatialaudio/nbsphinx/blob/master/NEWS.rst)
- [Commits](spatialaudio/nbsphinx@0.9.2...0.9.3)

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

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

docs/requirements.txt

@@ -1,5 +1,5 @@
 ipykernel==6.21.2
-nbsphinx==0.9.2
+nbsphinx==0.9.3
 pydata-sphinx-theme==0.13.3
 sphinx==7.0.1
 sphinx-gallery==0.13.0