message: remove let binding in conf test
diff: @@ -411,7 +411,7 @@ mod tests {
  fn headless_encode_round_trip() {
  let c1 = conf::Conf::new();
  let mut writer = Vec::new();
  - let _c = c1.to_toml_file(&mut writer).unwrap();
  + c1.to_toml_file(&mut writer).unwrap();
  let mut reader = writer.as_slice();
  let c2 = conf::Conf::from_toml_file(&mut reader).unwrap();
  assert_eq!(c1, c2);
  