[test] Unstable test CoordinatorEventManagerTest.testMetricsUpdatedImmediatelyOnStartup

[github-actions]

https://github.com/apache/fluss/actions/runs/24834425447/job/72690838319

[ERROR] org.apache.fluss.server.coordinator.event.CoordinatorEventManagerTest.testMetricsUpdatedImmediatelyOnStartup  Time elapsed: 0.004 s  <<< FAILURE!
org.opentest4j.AssertionFailedError: