Fix Stockfish version in card (19)

README.md

@@ -26,7 +26,7 @@ Code, training logs and write-ups: <https://github.com/AshishSinha5/chess-lm>
 
 - **Loss per move:** the cross-entropy on held-out games, in nats, per move token (lower is better).
 - **Legal moves:** how often the top-scoring move is legal, with no legal-move mask. One random position from each of 5,000 held-out games.
-- **Elo vs Stockfish:** the Elo estimate from games against Stockfish 16 at limited `UCI_Elo`. It uses Stockfish's nominal scale. It is **not** a Lichess or FIDE rating.
+- **Elo vs Stockfish:** the Elo estimate from games against Stockfish 19 at limited `UCI_Elo`. It uses Stockfish's nominal scale. It is **not** a Lichess or FIDE rating.
 
 All four files are the 1B-token runs with seed 0. Each folder holds `model.safetensors` (weights only) and `config.json`.