Bump auto-changelog from 2.5.1 to 2.6.0

Bumps [auto-changelog](https://github.com/CookPete/auto-changelog) from 2.5.1 to 2.6.0.
- [Changelog](https://github.com/cookpete/auto-changelog/blob/master/CHANGELOG.md)
- [Commits](cookpete/auto-changelog@v2.5.1...v2.6.0)

---
updated-dependencies:
- dependency-name: auto-changelog
  dependency-version: 2.6.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]