Bump supported CC API version to 2.256.0

Author: Kehrlann

cloudfoundry-client/src/main/java/org/cloudfoundry/client/CloudFoundryClient.java

@@ -81,7 +81,7 @@ public interface CloudFoundryClient {
     /**
      * The currently supported Cloud Controller API version
      */
-    String SUPPORTED_API_VERSION = "2.254.0";
+    String SUPPORTED_API_VERSION = "2.256.0";
 
     /**
      * Main entry point to the Cloud Foundry Application Usage Events Client API