test history: don't flush root node if there is not much output (IDEA-157793)

java/execution/impl/src/com/intellij/execution/JavaTestFrameworkRunnableState.java

@@ -156,7 +156,6 @@ public abstract class JavaTestFrameworkRunnableState<T extends
       @Override
       public void processTerminated(ProcessEvent event) {
         Runnable runnable = () -> {
-          root.flush();
           deleteTempFiles();
           clear();
         };