Bump phpstan/phpstan from 1.6.7 to 1.6.8

Bumps [phpstan/phpstan](https://github.com/phpstan/phpstan) from 1.6.7 to 1.6.8.
- [Release notes](https://github.com/phpstan/phpstan/releases)
- [Changelog](https://github.com/phpstan/phpstan/blob/1.7.x/CHANGELOG.md)
- [Commits](phpstan/phpstan@1.6.7...1.6.8)

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

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

composer.json

@@ -23,7 +23,7 @@
     "php-standard-library/psalm-plugin": "^1.1",
     "phpspec/prophecy": "^1.15",
     "phpspec/prophecy-phpunit": "^2.0.1",
-    "phpstan/phpstan": "^1.6.7",
+    "phpstan/phpstan": "^1.6.8",
     "phpunit/phpunit": "^9.5.19",
     "psalm/plugin-phpunit": "^0.16.1",
     "roave/backward-compatibility-check": "^6",