Update phpstan/phpstan requirement from ^1.10 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@1.10.0...2.0.3)

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

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

composer.json

@@ -23,7 +23,7 @@
         "mockery/mockery": "^1.4",
         "php-coveralls/php-coveralls": "^2.0",
         "phpcompatibility/php-compatibility": "*",
-        "phpstan/phpstan": "^1.10",
+        "phpstan/phpstan": "^2.0",
         "squizlabs/php_codesniffer": "*"
     },
     "autoload": {