Bump yoast/phpunit-polyfills from 1.1.0 to 3.1.1 (#98)

Bumps [yoast/phpunit-polyfills](https://github.com/Yoast/PHPUnit-Polyfills) from 1.1.0 to 3.1.1.
- [Release notes](https://github.com/Yoast/PHPUnit-Polyfills/releases)
- [Changelog](https://github.com/Yoast/PHPUnit-Polyfills/blob/3.x/CHANGELOG.md)
- [Commits](Yoast/PHPUnit-Polyfills@1.1.0...3.1.1)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

composer.json

@@ -15,7 +15,7 @@
       "pantheon-systems/pantheon-wp-coding-standards": "^2.0",
       "pantheon-systems/pantheon-wordpress-upstream-tests": "dev-master",
       "phpunit/phpunit": "^9",
-      "yoast/phpunit-polyfills": "^1.0",
+      "yoast/phpunit-polyfills": "^3.1",
     "pantheon-systems/wpunit-helpers": "^2.0"
   },
   "scripts": {