Bump phpunit/phpunit from 9.0.2 to 9.1.0

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 9.0.2 to 9.1.0.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/master/ChangeLog-9.1.md)
- [Commits](sebastianbergmann/phpunit@9.0.2...9.1.0)

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