Fix flaky test: TestStructuredStreaming.testStructuredStreaming

{code:java}
Error:  Tests run: 16, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 195.83 s <<< FAILURE! - in org.apache.hudi.functional.TestStructuredStreaming
Error:  testStructuredStreaming{HoodieTableType}[1]  Time elapsed: 6.602 s  <<< ERROR!
java.util.concurrent.ExecutionException: Boxed Error
    at scala.concurrent.impl.Promise$.resolver(Promise.scala:87)
    at scala.concurrent.impl.Promise$.scala$concurrent$impl$Promise$$resolveTry(Promise.scala:79)
    at scala.concurrent.impl.Promise$DefaultPromise.tryComplete(Promise.scala:284)
    at scala.concurrent.Promise.complete(Promise.scala:53)
    at scala.concurrent.Promise.complete$(Promise.scala:52)
    at scala.concurrent.impl.Promise$DefaultPromise.complete(Promise.scala:187)
    at scala.concurrent.impl.Promise.$anonfun$transform$1(Promise.scala:33)
    at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:64)
    at java.base/java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1395)
    at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373)
    at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182)
    at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655)
    at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622)
    at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165)
Caused by: java.lang.AssertionError: assertion failed
    at scala.Predef$.assert(Predef.scala:208)
    at org.apache.hudi.functional.TestStructuredStreaming.$anonfun$structuredStreamingTestRunner$1(TestStructuredStreaming.scala:151)
    at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
    at scala.concurrent.Future$.$anonfun$apply$1(Future.scala:659)
    at scala.util.Success.$anonfun$map$1(Try.scala:255)
    at scala.util.Success.map(Try.scala:213)
    at scala.concurrent.Future.$anonfun$map$1(Future.scala:292)
    at scala.concurrent.impl.Promise.liftedTree1$1(Promise.scala:33)
    ... 8 more {code}

## JIRA info

- Link: https://issues.apache.org/jira/browse/HUDI-8874
- Type: Bug
- Fix version(s):
- 1.1.0