Fix missing annotation warning in ocpp-v1_6

The ChangeAvailabilityConfirmation() constructor was marked deprecated
in the Javadoc, but missing the annotation.

Add the missing annotation.

Author: robert-s-ubi

ocpp-v1_6/src/main/java/eu/chargetime/ocpp/model/core/ChangeAvailabilityConfirmation.java

@@ -46,6 +46,7 @@ public class ChangeAvailabilityConfirmation extends Confirmation {
    * @deprecated use {@link #ChangeAvailabilityConfirmation(AvailabilityStatus)} to be sure to set
    *     required fields
    */
+  @Deprecated
   public ChangeAvailabilityConfirmation() {}
 
   /**