Bump nbsphinx from 0.7.1 to 0.8.6

Bumps [nbsphinx](https://github.com/spatialaudio/nbsphinx) from 0.7.1 to 0.8.6.
- [Release notes](https://github.com/spatialaudio/nbsphinx/releases)
- [Changelog](https://github.com/spatialaudio/nbsphinx/blob/master/NEWS.rst)
- [Commits](spatialaudio/nbsphinx@0.7.1...0.8.6)

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

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

Author: dependabot[bot]

requirements-dev.txt

@@ -2,7 +2,7 @@ ipython==7.16.1
 Sphinx==4.0.2
 sphinx-autobuild==0.7.1
 sphinxcontrib-fulltoc==1.2.0
-nbsphinx==0.7.1
+nbsphinx==0.8.6
 
 # https://github.com/pydata/xarray/issues/5299#issuecomment-840730954
 jinja2<3.0