[Flaky Test] org.apache.uniffle.test.GetReaderTest

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)

### Search before asking

- [X] I have searched in the [issues](https://github.com/apache/incubator-uniffle/issues?q=is%3Aissue) and found no similar issues.

### Describe the flaky test

Error: Tests run: 1, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 4.589 s <<< FAILURE! - in org.apache.uniffle.test.GetReaderTest
Error: test Time elapsed: 3.726 s <<< FAILURE!
org.opentest4j.AssertionFailedError: expected: <2> but was: <0>
at org.junit.jupiter.api.AssertionUtils.fail(AssertionUtils.java:55)
at org.junit.jupiter.api.AssertionUtils.failNotEqual(AssertionUtils.java:62)
at org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:150)
at org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:145)
at org.junit.jupiter.api.Assertions.assertEquals(Assertions.java:527)
at org.apache.uniffle.test.GetReaderTest.test(GetReaderTest.java:171)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

### Actions URL

https://github.com/apache/incubator-uniffle/pull/2005

https://github.com/apache/incubator-uniffle/actions/runs/10209746228/job/28248239028?pr=2005

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

Start by running org.apache.uniffle.test.GetReaderTest and inspect the failing assertion at GetReaderTest.java:171. Use the reported Actions run and pull request #2005 to compare the failure with a passing run. Done means the test reliably observes the expected value of 2 without introducing intermittent failures.

Written by the indexing model from the issue text.