Merge pull request #2068 from Niconal

* pr/2068:
  Polish "Add missing [ in toString of WebSocketMessageBrokerStats"
  Add missing [ in toString of WebSocketMessageBrokerStats

spring-websocket/src/main/java/org/springframework/web/socket/config/WebSocketMessageBrokerStats.java

 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -199,7 +199,7 @@ public class WebSocketMessageBrokerStats {
 				", stompSubProtocol[" + getStompSubProtocolStatsInfo() + "]" +
 				", stompBrokerRelay[" + getStompBrokerRelayStatsInfo() + "]" +
 				", inboundChannel[" + getClientInboundExecutorStatsInfo() + "]" +
-				", outboundChannel" + getClientOutboundExecutorStatsInfo() + "]" +
+				", outboundChannel[" + getClientOutboundExecutorStatsInfo() + "]" +
 				", sockJsScheduler[" + getSockJsTaskSchedulerStatsInfo() + "]";
 	}