Bump sphinx from 5.0.0 to 8.1.3

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 5.0.0 to 8.1.3.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/v8.1.3/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v5.0.0...v8.1.3)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-version: 8.1.3
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

python/dev_require.txt

@@ -23,7 +23,7 @@ prospector
 black
 
 # The following packages are only required for building documentation and are not required at runtime
-sphinx==7.0.0
+sphinx==8.1.3
 sphinx_rtd_theme
 nbsphinx
 numpydoc==0.8

python/require.txt

@@ -22,7 +22,7 @@ rstcheck
 prospector
 
 # The following packages are only required for building documentation and are not required at runtime
-sphinx==5.0.0
+sphinx==8.1.3
 sphinx_rtd_theme
 nbsphinx
 numpydoc==0.8