Update phpstan/phpstan requirement from ^1.4.8 to ^2.0.4

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@1.4.8...2.0.4)

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

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

composer.json

@@ -50,7 +50,7 @@
 	},
 	"require-dev": {
 		"vimeo/psalm": "^5.0.0",
-		"phpstan/phpstan": "^1.4.8",
+		"phpstan/phpstan": "^2.0.4",
 		"mediawiki/mediawiki-codesniffer": "39.0.0"
 	},
 	"autoload": {