chore(deps): bump date-holidays in /.github/workflows/holiday-generator (#840)

Bumps [date-holidays](https://github.com/commenthol/date-holidays) from 3.26.2 to 3.26.4.
- [Changelog](https://github.com/commenthol/date-holidays/blob/master/CHANGELOG.md)
- [Commits](commenthol/date-holidays@v3.26.2...v3.26.4)

---
updated-dependencies:
- dependency-name: date-holidays
  dependency-version: 3.26.4
  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]