[Form] Allow symfony/service-contracts v2.

Author: derrabus

composer.json

@@ -23,7 +23,7 @@
         "symfony/polyfill-ctype": "~1.8",
         "symfony/polyfill-mbstring": "~1.0",
         "symfony/property-access": "^3.4|^4.0|^5.0",
-        "symfony/service-contracts": "~1.1"
+        "symfony/service-contracts": "^1.1|^2"
     },
     "require-dev": {
         "doctrine/collections": "~1.0",