Bump phpstan/phpstan from 0.9.2 to 0.9.3

Bumps [phpstan/phpstan](https://github.com/phpstan/phpstan) from 0.9.2 to 0.9.3.
- [Release notes](https://github.com/phpstan/phpstan/releases)
- [Commits](phpstan/phpstan@0.9.2...0.9.3)

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