Bump sphinxcontrib-spelling from 7.3.1 to 7.3.2 (#268)

Bumps [sphinxcontrib-spelling](https://github.com/sphinx-contrib/spelling) from 7.3.1 to 7.3.2.
- [Release notes](https://github.com/sphinx-contrib/spelling/releases)
- [Commits](sphinx-contrib/spelling@7.3.1...7.3.2)

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

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

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

Author: dependabot[bot]

requirements/doc-spelling.txt

@@ -1,2 +1,2 @@
 -r doc.txt
-sphinxcontrib-spelling==7.3.1; platform_system!="Windows"  # We only use it in Travis CI
+sphinxcontrib-spelling==7.3.2; platform_system!="Windows"  # We only use it in Travis CI