Bump sphinx from 4.0.1 to 4.0.2 (#35)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 4.0.1 to 4.0.2.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/4.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v4.0.1...v4.0.2)

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

docs/requirements.txt

@@ -1,3 +1,3 @@
-sphinx==4.0.1
+sphinx==4.0.2
 sphinx_rtd_theme==0.5.2
 m2r2==0.2.7