AsyncResultSetImplTest.testCallbackIsNotCalledWhilePaused is flaky on Windows build

Build error:

```
Error:  Tests run: 15, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0.571 s <<< FAILURE! - in com.google.cloud.spanner.AsyncResultSetImplTest
Error:  com.google.cloud.spanner.AsyncResultSetImplTest.testCallbackIsNotCalledWhilePaused  Time elapsed: 0.478 s  <<< FAILURE!
com.google.common.truth.ComparisonFailureWithFacts: 
expected: 100
but was : 99
	at com.google.cloud.spanner.AsyncResultSetImplTest.testCallbackIsNotCalledWhilePaused(AsyncResultSetImplTest.java:372)
```


Description