build(deps-dev): update infection/infection requirement from ^0.21.2 to ^0.21.4 (#42)

Author: dependabot-preview[bot]

composer.json

@@ -20,7 +20,7 @@
     "require-dev": {
         "doctrine/coding-standard": "^8.2",
         "ergebnis/composer-normalize": "^2.13",
-        "infection/infection": "^0.21.2",
+        "infection/infection": "^0.21.4",
         "phpstan/extension-installer": "^1.1",
         "phpstan/phpstan": "^0.12.79",
         "phpstan/phpstan-phpunit": "^0.12.18",