chore(deps): bump date-holidays in /.github/workflows/holiday-generator (#962)

Bumps [date-holidays](https://github.com/commenthol/date-holidays) from 3.26.5 to 3.26.6.
- [Changelog](https://github.com/commenthol/date-holidays/blob/master/CHANGELOG.md)
- [Commits](commenthol/date-holidays@v3.26.5...v3.26.6)

---
updated-dependencies:
- dependency-name: date-holidays
  dependency-version: 3.26.6
  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]