Revert "Fix flaky test StreamingDataflowWorkerTest"

[Abacn]

Reverts #28173

The enabled test has been flaky on both Jenkins and actions. e,g, https://ci-beam.apache.org/job/beam_PreCommit_Java_Cron/7319/testReport/junit/org.apache.beam.runners.dataflow.worker/StreamingDataflowWorkerTest/testMaxThreadMetric_0___streamingEngine_false__/

and the commit trigger seeing this quite often: https://ci-beam.apache.org/job/beam_PreCommit_Java_Commit/

Stacktrace
java.lang.AssertionError: expected:<1000> but was:<0>
	at org.junit.Assert.fail(Assert.java:89)
	at org.junit.Assert.failNotEquals(Assert.java:835)
	at org.junit.Assert.assertEquals(Assert.java:647)
	at org.junit.Assert.assertEquals(Assert.java:633)
	at org.apache.beam.runners.dataflow.worker.StreamingDataflowWorkerTest.testMaxThreadMetric(StreamingDataflowWorkerTest.java:2935)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

[Abacn]

R: @tvalentyn
CC: @olalamichelle thanks willing to dig into this in the original PR. The branch hash is stay so we can always come back and investigate. For now I would propose this change to de-noise purpose

[github-actions]

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control

[tvalentyn]

LGTM, thanks. Sorry about the noise it caused.

[Abacn]

Ironically the PreCommit GitHub Action still fails this test even it's reverted in this PR: https://github.com/apache/beam/actions/runs/6174695355/job/16759856184?pr=28434

> Task :runners:google-cloud-dataflow-java:worker:test

org.apache.beam.runners.dataflow.worker.StreamingDataflowWorkerTest > testMaxThreadMetric[0: [streamingEngine=false]] FAILED
    java.lang.AssertionError at StreamingDataflowWorkerTest.java:2935