Bump sphinx-github-changelog from 1.2.0 to 1.2.1

Bumps [sphinx-github-changelog](https://github.com/ewjoachim/sphinx-github-changelog) from 1.2.0 to 1.2.1.
- [Release notes](https://github.com/ewjoachim/sphinx-github-changelog/releases)
- [Changelog](https://github.com/ewjoachim/sphinx-github-changelog/blob/main/CHANGELOG.rst)
- [Commits](ewjoachim/sphinx-github-changelog@1.2.0...1.2.1)

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

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