composer(deps-dev): Bump phpstan/phpstan from 1.9.3 to 1.9.4

Bumps [phpstan/phpstan](https://github.com/phpstan/phpstan) from 1.9.3 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@1.9.3...1.9.4)

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

Signed-off-by: dependabot[bot] <support@github.com>

composer.json

@@ -39,7 +39,7 @@
     "ergebnis/phpstan-rules": "^1.0.0",
     "infection/infection": "~0.26.16",
     "phpstan/extension-installer": "^1.2.0",
-    "phpstan/phpstan": "^1.9.2",
+    "phpstan/phpstan": "^1.9.4",
     "phpstan/phpstan-deprecation-rules": "^1.1.1",
     "phpstan/phpstan-doctrine": "^1.3.27",
     "phpstan/phpstan-phpunit": "^1.3.2",