composer(deps-dev): bump phpstan/phpstan from 1.12.0 to 1.12.1 (#1833)

Bumps [phpstan/phpstan](/~https://github.com/phpstan/phpstan) from 1.12.0 to 1.12.1.
- [Release notes](/~https://github.com/phpstan/phpstan/releases)
- [Changelog](/~https://github.com/phpstan/phpstan/blob/1.12.x/CHANGELOG.md)
- [Commits](phpstan/phpstan@1.12.0...1.12.1)

---
updated-dependencies:
- dependency-name: phpstan/phpstan
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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