Composer: Update yoast/phpunit-polyfills requirement

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/2.x/CHANGELOG.md)
- [Commits](Yoast/PHPUnit-Polyfills@1.1.1...2.0.1)

---
updated-dependencies:
- dependency-name: yoast/phpunit-polyfills
  dependency-type: direct:production
...

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

composer.json

@@ -30,7 +30,7 @@
 	"require": {
 		"php": ">=5.6",
 		"brain/monkey": "^2.6.1",
-		"yoast/phpunit-polyfills": "^1.1.1"
+		"yoast/phpunit-polyfills": "^2.0.1"
 	},
 	"require-dev": {
 		"php-parallel-lint/php-console-highlighter": "^1.0.0",