Bump sphinx from 4.2.0 to 4.3.1

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 4.2.0 to 4.3.1.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/4.x/CHANGES)
- [Commits](https://github.com/sphinx-doc/sphinx/compare/v4.2.0...v4.3.1)

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

Signed-off-by: dependabot[bot] <support@github.com>

requirements/dev.txt

@@ -106,7 +106,7 @@ six==1.16.0
     #   virtualenv
 snowballstemmer==2.1.0
     # via sphinx
-sphinx==4.2.0
+sphinx==4.3.1
     # via
     #   -r requirements/docs.in
     #   pallets-sphinx-themes

requirements/docs.txt

@@ -42,7 +42,7 @@ requests==2.26.0
     # via sphinx
 snowballstemmer==2.1.0
     # via sphinx
-sphinx==4.2.0
+sphinx==4.3.1
     # via
     #   -r requirements/docs.in
     #   pallets-sphinx-themes