Bump squizlabs/php_codesniffer from 3.8.0 to 3.9.0 (#280)

Bumps [squizlabs/php_codesniffer](https://github.com/PHPCSStandards/PHP_CodeSniffer) from 3.8.0 to 3.9.0.
- [Release notes](https://github.com/PHPCSStandards/PHP_CodeSniffer/releases)
- [Changelog](https://github.com/PHPCSStandards/PHP_CodeSniffer/blob/master/CHANGELOG.md)
- [Commits](PHPCSStandards/PHP_CodeSniffer@3.8.0...3.9.0)

---
updated-dependencies:
- dependency-name: squizlabs/php_codesniffer
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]