Remove @OverRide from the RabbitAdmin.initialize

https://build.spring.io/browse/AMQP-AMQP20X-3/

The `AmqpAdmin.initialize()` is there since `2.1`

**Cherry-pick to 1.7.x**

Author: artembilan

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/core/RabbitAdmin.java

@@ -430,7 +430,6 @@ public void afterPropertiesSet() {
 	 * Declares all the exchanges, queues and bindings in the enclosing application context, if any. It should be safe
 	 * (but unnecessary) to call this method more than once.
 	 */
-	@Override
 	public void initialize() {
 
 		if (this.applicationContext == null) {