1.15.0: Update github_changelog_generator requirement
Updates the requirements on [github_changelog_generator](https://github.com/github-changelog-generator/Github-Changelog-Generator) to permit the latest version. - [Release notes](https://github.com/github-changelog-generator/Github-Changelog-Generator/releases) - [Changelog](https://github.com/github-changelog-generator/github-changelog-generator/blob/master/CHANGELOG.md) - [Commits](https://github.com/github-changelog-generator/Github-Changelog-Generator/compare/v1.15.0.pre.rc...v1.15.0) Signed-off-by: dependabot-preview[bot] <[email protected]>