Bump phpoffice/phpspreadsheet from 2.3.5 to 2.3.7

Bumps [phpoffice/phpspreadsheet](https://github.com/PHPOffice/PhpSpreadsheet) from 2.3.5 to 2.3.7.
- [Release notes](https://github.com/PHPOffice/PhpSpreadsheet/releases)
- [Changelog](https://github.com/PHPOffice/PhpSpreadsheet/blob/2.3.7/CHANGELOG.md)
- [Commits](PHPOffice/PhpSpreadsheet@2.3.5...2.3.7)

---
updated-dependencies:
- dependency-name: phpoffice/phpspreadsheet
  dependency-type: direct:production
...

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Author: dependabot[bot]