[DEPS]: Bump yoast/phpunit-polyfills from 3.1.1 to 4.0.0

Bumps [yoast/phpunit-polyfills](https://github.com/Yoast/PHPUnit-Polyfills) from 3.1.1 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@3.1.1...4.0.0)

---
updated-dependencies:
- dependency-name: yoast/phpunit-polyfills
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

composer.json

@@ -61,7 +61,7 @@
         "phpunit/phpunit": "^9",
         "szepeviktor/phpstan-wordpress": "^1.3",
         "wp-phpunit/wp-phpunit": "^6.6",
-        "yoast/phpunit-polyfills": "^3"
+        "yoast/phpunit-polyfills": "^4"
     },
     "extra": {
         "wordpress-install-dir": "wp",