MINOR: Fix misleading log-line (#14643)

After finishing restoration, we should only log the active tasks. Standby tasks are not part of restoration and it can be confusing to see them show up on this log message.

Reviewers: Matthias J. Sax <matthias@confluent.io>

streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamThread.java

@@ -1030,8 +1030,8 @@ public class StreamThread extends Thread {
             log.debug("State is {}; initializing tasks if necessary", stateSnapshot);
 
             if (taskManager.tryToCompleteRestoration(now, offsetResetter)) {
-                log.info("Restoration took {} ms for all tasks {}", time.milliseconds() - lastPartitionAssignedMs,
-                    taskManager.allTasks().keySet());
+                log.info("Restoration took {} ms for all active tasks {}", time.milliseconds() - lastPartitionAssignedMs,
+                    taskManager.activeTaskIds());
                 setState(State.RUNNING);
             }