Bump xos libraries to version 4.0.0

Change-Id: Ibd20e72a594fa88df77904acc70e1f852ea2e15e
diff --git a/xos/synchronizer/config.yaml b/xos/synchronizer/config.yaml
index 0f7699e..939770d 100644
--- a/xos/synchronizer/config.yaml
+++ b/xos/synchronizer/config.yaml
@@ -15,7 +15,7 @@
 
 
 name: rcord
-core_version: ">=3.2.8"
+core_version: ">=4.0.0"
 required_models:
   - RCORDService
   - RCORDSubscriber