Remove invalid subscriptionName property for service bus topic output

Author: PramodValavala-MSFT

src/main/java/com/microsoft/azure/functions/annotation/ServiceBusTopicOutput.java

@@ -56,13 +56,6 @@
    */
   String topicName();
 
-  /**
-   * Defines the subscription name of the Service Bus topic to which to write.
-   * 
-   * @return The Service Bus topic subscription name string.
-   */
-  String subscriptionName();
-
   /**
    * Defines the app setting name that contains the Service Bus connection string.
    *