Fix flaky executor test (#5658)

instrumentation/executors/testing/src/main/java/io/opentelemetry/javaagent/instrumentation/javaconcurrent/AbstractExecutorServiceTest.java

@@ -150,7 +150,7 @@ protected final void executeAndCancelTasks(Function<U, Future<?>> task) {
  // we do not really have a good way for attributing work to correct parent span
  // if we reuse Callable/Runnable.
  // Solution for now is to never reuse a Callable/Runnable.
- U child = newTask(true, true);
+ U child = newTask(false, true);
  children.add(child);
  Future<?> f = task.apply(child);
  jobFutures.add(f);