Fix package name - avoid warning about invalid javadoc.

Partially resolves spring-cloud#156

Author: onobc

multi-io-samples/ticktock/multi-output-time-kafka/src/main/java/org/springframework/cloud/stream/app/time/source/kafka/MultiOutputTimeSourceKafkaApplication.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package org.springframework.cloud.stream.app.time.source.rabbit;
+package org.springframework.cloud.stream.app.time.source.kafka;
 
 import java.util.Date;
 import java.util.function.Supplier;