Update yoast/phpunit-polyfills requirement from ^3.0 to ^4.0

Updates the requirements on [yoast/phpunit-polyfills](https://github.com/Yoast/PHPUnit-Polyfills) to permit the latest version.
- [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@3.0.0...4.0.0)

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

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

Author: dependabot[bot]

composer.json

@@ -23,7 +23,7 @@
 	},
 	"require-dev": {
 		"phpunit/phpunit": "^9.0",
-		"yoast/phpunit-polyfills": "^3.0",
+		"yoast/phpunit-polyfills": "^4.0",
 		"dealerdirect/phpcodesniffer-composer-installer": "^1.0",
 		"squizlabs/php_codesniffer": "^3.0",
 		"wp-coding-standards/wpcs": "^3.0",