Regard the release when the APIs became deprecated as Cardinal

Change-Id: I072fa33a2a70baa7466d7a0dc5067191476be0f3
diff --git a/apps/optical/src/main/java/org/onosproject/optical/cfg/OpticalNetworkConfig.java b/apps/optical/src/main/java/org/onosproject/optical/cfg/OpticalNetworkConfig.java
index bfc8ab9..f3f8d17 100644
--- a/apps/optical/src/main/java/org/onosproject/optical/cfg/OpticalNetworkConfig.java
+++ b/apps/optical/src/main/java/org/onosproject/optical/cfg/OpticalNetworkConfig.java
@@ -23,6 +23,8 @@
 
 /**
  * Public class corresponding to JSON described data model.
+ *
+ * @deprecated in Cardinal Release
  */
 @Deprecated
 public class OpticalNetworkConfig {