composer(deps-dev): update phpstan/phpstan requirement (#26)

Updates the requirements on [phpstan/phpstan](https://github.com/phpstan/phpstan) to permit the latest version.
- [Release notes](https://github.com/phpstan/phpstan/releases)
- [Changelog](https://github.com/phpstan/phpstan/blob/1.9.x/CHANGELOG.md)
- [Commits](phpstan/phpstan@1.9.6...1.9.7)

---
updated-dependencies:
- dependency-name: phpstan/phpstan
  dependency-type: direct:development
...

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

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

Author: dependabot[bot]

composer.json

@@ -33,7 +33,7 @@
     "ext-xmlwriter": "*",
     "mimmi20/coding-standard": "^3.0.24",
     "phpstan/extension-installer": "^1.2.0",
-    "phpstan/phpstan": "^1.9.6",
+    "phpstan/phpstan": "^1.9.7",
     "phpstan/phpstan-deprecation-rules": "^1.1.1",
     "phpstan/phpstan-phpunit": "^1.3.3",
     "phpunit/phpunit": "^9.5.27"