Bump phpstan/phpstan from 1.8.6 to 1.9.4 (#182)

Bumps [phpstan/phpstan](https://github.com/phpstan/phpstan) from 1.8.6 to 1.9.4.
- [Release notes](https://github.com/phpstan/phpstan/releases)
- [Changelog](https://github.com/phpstan/phpstan/blob/1.9.x/CHANGELOG.md)
- [Commits](phpstan/phpstan@1.8.6...1.9.4)

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

Signed-off-by: dependabot[bot] <[email protected]>

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]