update the silex version to 2.2.0 and doctrine to 2.6.2 (#2996)

frameworks/PHP/silex/composer.json

@@ -1,6 +1,6 @@
 {
     "require": {
-        "silex/silex": "1.0.*@dev",
-        "doctrine/dbal": "2.4.*@dev"
+        "silex/silex": "2.2.0",
+        "doctrine/dbal": "2.6.2"
     }
 }