chore: fix the if logic of deprecated usage in stats logger (#407)

Author: dhh1995

areal/utils/stats_logger.py

@@ -20,7 +20,7 @@
 class StatsLogger:
 
     def __init__(self, config: BaseExperimentConfig, ft_spec: FinetuneSpec):
-        if not isinstance(config, StatsLoggerConfig):
+        if isinstance(config, StatsLoggerConfig):
             raise ValueError(
                 "Passing config.stats_logger as the config is deprecated. "
                 "Please pass the full config instead."