Remove unused Log object from MessageHeaderAccessor

Issue: SPR-15045
(cherry picked from commit 5c48daa)

Author: jhoeller

spring-messaging/src/main/java/org/springframework/messaging/support/MessageHeaderAccessor.java

@@ -24,9 +24,6 @@
 import java.util.Map;
 import java.util.UUID;
 
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
-
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.MessageHeaders;
@@ -123,8 +120,6 @@ public class MessageHeaderAccessor {
 	};
 
 
-	protected final Log logger = LogFactory.getLog(getClass());
-
 	private final MutableMessageHeaders headers;
 
 	private boolean leaveMutable = false;