Bump nbsphinx from 0.9.6 to 0.9.7

Bumps [nbsphinx](https://github.com/spatialaudio/nbsphinx) from 0.9.6 to 0.9.7.
- [Release notes](https://github.com/spatialaudio/nbsphinx/releases)
- [Changelog](https://github.com/spatialaudio/nbsphinx/blob/master/NEWS.rst)
- [Commits](spatialaudio/nbsphinx@0.9.6...0.9.7)

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

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

Author: dependabot[bot]