fix f string

src/backend.py

@@ -477,7 +477,7 @@ def evaluate(
                 # Reset also when the goal is achieved when using HER
                 if done and infos[0].get("is_success") is not None:
                     if verbose > 1:
-                        logger.info(f"Success? {infos[0].get("is_success", False)}")
+                        logger.info(f"Success? {infos[0].get('is_success', False)}")
 
                     if infos[0].get("is_success") is not None:
                         successes.append(infos[0].get("is_success", False))