Remove requirement for symfony/yaml

Author: chadicus

composer.json

@@ -11,8 +11,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": ">=6.0",
-        "squizlabs/php_codesniffer": "^3.3",
-        "symfony/yaml": ">=2.0.5"
+        "squizlabs/php_codesniffer": "^3.3"
     },
     "autoload": {
         "psr-4": { "SubjectivePHP\\Util\\": "src/" }