Fix version in ListenableFuture removal warning message

Author: artembilan

spring-integration-core/src/main/java/org/springframework/integration/gateway/GatewayProxyFactoryBean.java

@@ -544,7 +544,7 @@ else if (CompletableFuture.class.equals(returnType)) { // exact
 			else if (org.springframework.util.concurrent.ListenableFuture.class.equals(returnType)) {
 				logger.warn("The 'org.springframework.util.concurrent.ListenableFuture' is deprecated for removal." +
 						"The 'CompletableFuture' is recommended to be used instead." +
-						"The 'ListenableFuture' support will be removed in Spring Integration 7.0.");
+						"The 'ListenableFuture' support will be removed in Spring Integration 6.5.");
 				return ((org.springframework.core.task.AsyncListenableTaskExecutor) this.asyncExecutor)
 						.submitListenable(invoker::get);
 			}

spring-integration-core/src/main/java/org/springframework/integration/handler/AbstractMessageProducingHandler.java

@@ -427,7 +427,7 @@ private CompletableFuture<?> toCompletableFuture(Object reply) {
 		else {
 			logger.warn("The 'org.springframework.util.concurrent.ListenableFuture' is deprecated for removal." +
 					"The 'CompletableFuture' is recommended to be used instead." +
-					"The 'ListenableFuture' support will be removed in Spring Integration 7.0.");
+					"The 'ListenableFuture' support will be removed in Spring Integration 6.5.");
 			return ((org.springframework.util.concurrent.ListenableFuture<?>) reply).completable();
 		}
 	}