Remove serialVersionUIDs in spring-messaging Exc.

Prior to this commit, several spring-messaging exceptions
had defined serialVersionUIDs. Those exception aren't
supposed to leave the system via Java serialization; also,
their deserialization is supported only against the same
version of Spring.

Issue: SPR-11339

spring-messaging/src/main/java/org/springframework/messaging/MessageHandlingException.java

@@ -22,11 +22,9 @@ package org.springframework.messaging;
  * @author Mark Fisher
  * @since 4.0
  */
+@SuppressWarnings("serial")
 public class MessageHandlingException extends MessagingException {
 
-	private static final long serialVersionUID = 690969923668400297L;
-
-
 	public MessageHandlingException(Message<?> message, String description) {
 		super(message, description);
 	}

spring-messaging/src/main/java/org/springframework/messaging/simp/annotation/support/MissingSessionUserException.java

@@ -23,11 +23,9 @@ import org.springframework.messaging.MessagingException;
  * @author Rossen Stoyanchev
  * @since 4.0
  */
+@SuppressWarnings("serial")
 public class MissingSessionUserException extends MessagingException {
 
-	private static final long serialVersionUID = -6905878930083523161L;
-
-
 	public MissingSessionUserException(Message<?> message) {
 		super(message, "No \"user\" header in message");
 	}