message: Fix inequality in "stale mtime" log messages
diff: @@ -1194,7 +1194,7 @@ impl StaleItem {
  } => {
  info!("stale: changed {:?}", stale);
  info!(" (vs) {:?}", reference);
  - info!(" {:?} != {:?}", reference_mtime, stale_mtime);
  + info!(" {:?} < {:?}", reference_mtime, stale_mtime);
  }
  StaleItem::ChangedEnv {
  var,
  