Bump sphinx-github-changelog from 1.2.1 to 1.3.0 (#693)

Bumps [sphinx-github-changelog](https://github.com/ewjoachim/sphinx-github-changelog) from 1.2.1 to 1.3.0.
- [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@1.2.1...1.3.0)

---
updated-dependencies:
- dependency-name: sphinx-github-changelog
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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