use RC3 of sonata

Author: ElectricMaxxx

composer.json

@@ -14,7 +14,7 @@
     "require": {
         "php": "^5.6|^7.0",
         "symfony/framework-bundle": "^2.8|^3.0",
-        "sonata-project/doctrine-phpcr-admin-bundle": "2.0.0-RC2",
+        "sonata-project/doctrine-phpcr-admin-bundle": "2.0.0-RC3",
         "sonata-project/admin-bundle": "^3.6.0",
         "symfony-cmf/tree-browser-bundle": "^2.0"
     },