Bump numpydoc from 1.5.0 to 1.6.0 in /docs

Bumps [numpydoc](https://github.com/numpy/numpydoc) from 1.5.0 to 1.6.0.
- [Release notes](https://github.com/numpy/numpydoc/releases)
- [Changelog](https://github.com/numpy/numpydoc/blob/main/doc/release_notes.rst)
- [Commits](numpy/numpydoc@v1.5.0...v1.6.0)

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

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

docs/requirements.txt

@@ -1,4 +1,4 @@
 furo==2023.8.19
 sphinx==7.2.5
-numpydoc==1.5.0
+numpydoc==1.6.0
 sphinx_toolbox