build(deps): Bump phpoffice/phpspreadsheet from 1.29.1 to 1.29.8

Bumps [phpoffice/phpspreadsheet](https://github.com/PHPOffice/PhpSpreadsheet) from 1.29.1 to 1.29.8.
- [Release notes](https://github.com/PHPOffice/PhpSpreadsheet/releases)
- [Changelog](https://github.com/PHPOffice/PhpSpreadsheet/blob/1.29.8/CHANGELOG.md)
- [Commits](PHPOffice/PhpSpreadsheet@1.29.1...1.29.8)

---
updated-dependencies:
- dependency-name: phpoffice/phpspreadsheet
  dependency-type: indirect
...

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