Bump phpoffice/phpspreadsheet from 2.0.0 to 2.1.0 (#1283)

Bumps [phpoffice/phpspreadsheet](https://github.com/PHPOffice/PhpSpreadsheet) from 2.0.0 to 2.1.0.
- [Release notes](https://github.com/PHPOffice/PhpSpreadsheet/releases)
- [Changelog](https://github.com/PHPOffice/PhpSpreadsheet/blob/master/CHANGELOG.md)
- [Commits](PHPOffice/PhpSpreadsheet@2.0.0...2.1.0)

---
updated-dependencies:
- dependency-name: phpoffice/phpspreadsheet
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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