Bump sphinx from 5.1.1 to 5.2.1 in /requirements (#122)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 5.1.1 to 5.2.1.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/5.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v5.1.1...v5.2.1)

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

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

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

Author: dependabot[bot]

requirements/requirements_doc.txt

@@ -1,4 +1,4 @@
-Sphinx==5.1.1
+Sphinx==5.2.1
 numpydoc==1.4.0
 sphinx-copybutton==0.5.0
 sphinx-notfound-page==0.8.3