fix the bug on the trainer

fastNLP/core/trainer.py

@@ -829,12 +829,12 @@ class Trainer(object):
             self.best_metric_indicator = indicator_val
         else:
             if self.increase_better is True:
-                if indicator_val >= self.best_metric_indicator:
+                if indicator_val > self.best_metric_indicator:
                     self.best_metric_indicator = indicator_val
                 else:
                     is_better = False
             else:
-                if indicator_val <= self.best_metric_indicator:
+                if indicator_val < self.best_metric_indicator:
                     self.best_metric_indicator = indicator_val
                 else:
                     is_better = False