remove symfony/symfony dependency

Author: fbourigault

composer.json

@@ -29,8 +29,7 @@
         "php-http/message": "^1.4",
         "php-http/discovery": "^1.0",
         "twig/twig": "^1.18 || ^2.0",
-        "symfony/asset": "^2.8 || ^3.0",
-        "symfony/symfony": "2.8.27"
+        "symfony/asset": "^2.8 || ^3.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^4.8.35 || ^5.7 || ^6.1",