Fix flaky test testStaticWithSideEffectFullCompletion

[zhihaodev]

Test failures in github action: https://github.com/linkedin/parseq/actions/runs/16303725941/job/46050223728

The current test testStaticWithSideEffectFullCompletion assert that the task is not done immediately after invoking run:

    Task<Void> sideEffect = Task.withSideEffect(() -> slowSideEffect);
    run(sideEffect);
    assertFalse(sideEffect.isDone());

However, this may not be true in all environments and looks like in github action the task can be completed faster.
Removing the assertion to make the test stable in github action.