Fix constant reference in the Javadoc

Author: dmitry-timofeev

exonum-java-binding/common/src/main/java/com/exonum/binding/common/serialization/json/ZonedDateTimeJsonSerializer.java

@@ -33,8 +33,8 @@
 
 /**
  * {@link ZonedDateTime} string serializer. Used to serialize/deserialize ZonedDateTime values
- * from/to strings in the {@link ISO_ZONED_DATE_TIME} date-time format with offset and zone, such
- * as '2011-12-03T10:15:30+01:00[Europe/Paris]'.
+ * from/to strings in the {@link DateTimeFormatter#ISO_ZONED_DATE_TIME} date-time format with
+ * offset and zone, such as '2011-12-03T10:15:30+01:00[Europe/Paris]'.
  *
  * <p>All method arguments are non-null by default.
  */