message: update text detection examples
  remove unnecessary `?`
diff: @@ -70,7 +70,7 @@ fn main() -> Result<()> {
  let mut frame = Mat::default();
  while highgui::wait_key(1)? < 0 {
  cap.read(&mut frame)?;
  - if frame.empty()? {
  + if frame.empty() {
  highgui::wait_key(0)?;
  break;
  }
  