fix f string

src/backend.py

@@ -460,7 +460,7 @@ def evaluate(
                     episode_infos = infos[0].get("episode")
                     if episode_infos is not None:
                         logger.info(f"Atari Episode Score: {episode_infos['r']:.2f}")
-                        logger.info(f"Atari Episode Length {episode_infos["l"]}")
+                        logger.info(f"Atari Episode Length {episode_infos['l']}")
                         episode_rewards.append(episode_infos["r"])
                         episode_lengths.append(episode_infos["l"])