Bump sphinx from 6.1.1 to 6.1.3 in /requirements (microsoft#1008)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 6.1.1 to 6.1.3.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES)
- [Commits](sphinx-doc/sphinx@v6.1.1...v6.1.3)

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

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requirements/docs.txt

@@ -2,4 +2,4 @@
 ipython==8.8.0
 ipywidgets==8.0.4
 nbsphinx==0.8.11
-sphinx==6.1.1
+sphinx==6.1.3