chore:update dependencies (#35)

Co-authored-by: Nicolas Reynis <nicolas.reynis@iwd.io>

Author: nreynis

composer.json

@@ -16,10 +16,10 @@
     },
     "require": {
         "php": ">=7.0",
-        "symfony/http-kernel": "^3.0",
-        "symfony/serializer": "^3.0",
-        "symfony/property-access": "^3.0",
-        "symfony/yaml": "^3.0",
+        "symfony/http-kernel": "^4.0",
+        "symfony/serializer": "^4.0",
+        "symfony/property-access": "^4.0",
+        "symfony/yaml": "^4.0",
         "raml-org/raml-php-parser": "^4.6",
         "jrfnl/php-cast-to-type": "^2.0",
         "willdurand/negotiation": "^2.0",