Flaky test `TestMonitorSource > testStateRestore`

[manuzhang]

https://github.com/apache/iceberg/actions/runs/26314549114/job/77471777704

TestMonitorSource > testStateRestore(File, ClusterClient) FAILED
    java.util.concurrent.TimeoutException
        at org.apache.iceberg.flink.maintenance.operator.CollectingSink.poll(CollectingSink.java:83)
        at org.apache.iceberg.flink.maintenance.operator.TestMonitorSource.testStateRestore(TestMonitorSource.java:232)