Update yoast/phpunit-polyfills requirement

Updates the requirements on [yoast/phpunit-polyfills](https://github.com/Yoast/PHPUnit-Polyfills) to permit the latest version.

Updates `yoast/phpunit-polyfills` to 4.0.0
- [Release notes](https://github.com/Yoast/PHPUnit-Polyfills/releases)
- [Changelog](https://github.com/Yoast/PHPUnit-Polyfills/blob/4.x/CHANGELOG.md)
- [Commits](Yoast/PHPUnit-Polyfills@2.0.0...4.0.0)

---
updated-dependencies:
- dependency-name: yoast/phpunit-polyfills
  dependency-version: 4.0.0
  dependency-type: direct:development
  dependency-group: composer-dependencies
...

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

Author: dependabot[bot]

composer.json

@@ -26,7 +26,7 @@
 		"szepeviktor/phpstan-wordpress": "^2.0",
 		"php-stubs/wordpress-stubs": "^6.9",
 		"phpunit/phpunit": ">=6",
-		"yoast/phpunit-polyfills": "^2.0"
+		"yoast/phpunit-polyfills": "^4.0"
 	},
 	"config": {
 		"allow-plugins": {