message: fix: Fix the display of callback summaries
diff: @@ -116,7 +116,7 @@ impl<'a> InteractiveShell<'a> {
  elapsed.as_secs(),
  elapsed.subsec_nanos()
  );
  - println!("{:?}", summary);
  + println!("{}", summary);
  context.borrow_mut().history.push(summary.into()).unwrap_or_else(|err| {
  eprintln!("ion: history append: {}", err);
  });
  