Install just yoast/phpunit-polyfills without explicit phpunit dep

Author: adamziel

composer-ci-matrix-tests.json

@@ -23,9 +23,8 @@
         "ext-mbstring": "*"
     },
     "require-dev": {
-        "yoast/phpunit-polyfills": "2.0.0",
-        "phpcompatibility/php-compatibility": "10.x-dev",
-        "phpunit/phpunit": "^9.5"
+        "yoast/phpunit-polyfills": "^4.0.0",
+        "phpcompatibility/php-compatibility": "10.x-dev"
     },
     "autoload": {
         "exclude-from-classmap": [