Update Javadoc for CookieValue

See gh-26989

spring-web/src/main/java/org/springframework/web/bind/annotation/CookieValue.java

 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -25,11 +25,15 @@ import java.lang.annotation.Target;
 import org.springframework.core.annotation.AliasFor;
 
 /**
- * Annotation which indicates that a method parameter should be bound to an HTTP cookie.
+ * Annotation to indicate that a method parameter is bound to an HTTP cookie.
  *
  * <p>The method parameter may be declared as type {@link javax.servlet.http.Cookie}
  * or as cookie value type (String, int, etc.).
  *
+ * <p>Note that with spring-webmvc 5.3.x and earlier, the cookie value is URL
+ * decoded. This will be changed in 6.0 but in the mean, applications can also
+ * declare {@link javax.servlet.http.Cookie} to access the raw value.
+ *
  * @author Juergen Hoeller
  * @author Sam Brannen
  * @since 3.0