Update phpstan/phpstan requirement from ^1.4 to ^2.0

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/2.0.x/CHANGELOG.md)
- [Commits](phpstan/phpstan@1.4.0...2.0.1)

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

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

composer.json

@@ -28,7 +28,7 @@
   "require-dev": {
     "roave/security-advisories": "dev-latest",
     "phpunit/phpunit": "^8 || ^9",
-    "phpstan/phpstan": "^1.4"
+    "phpstan/phpstan": "^2.0"
   },
   "config": {
     "allow-plugins": {