Merge pull request #32266 from vespa-engine/balder/avoid-java21-this-…

…escape-warning-17

Avoid this escape

vespaclient-core/src/main/java/com/yahoo/feedapi/MessagePropertyProcessor.java

@@ -17,7 +17,7 @@
  * Utility class for assigning properties to messages, either from implicit
  * config values or from explicit values in requests.
  */
-public class MessagePropertyProcessor implements ConfigSubscriber.SingleSubscriber<FeederConfig> {
+public final class MessagePropertyProcessor implements ConfigSubscriber.SingleSubscriber<FeederConfig> {
 
     private static final Logger log = Logger.getLogger(MessagePropertyProcessor.class.getName());
     private static final boolean defaultCreateIfNonExistent = false;