Mark MediaTypeNotSupportedStatusException as deprecated

Closes gh-24743

spring-web/src/main/java/org/springframework/web/server/MediaTypeNotSupportedStatusException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -27,7 +27,10 @@ import org.springframework.http.MediaType;
  *
  * @author Rossen Stoyanchev
  * @since 5.0
+ * @deprecated in favor of {@link UnsupportedMediaTypeStatusException},
+ * with this class never thrown by Spring code and to be removed in 5.3
  */
+@Deprecated
 @SuppressWarnings("serial")
 public class MediaTypeNotSupportedStatusException extends ResponseStatusException {