fix: fix typo

modeling_bert.py

@@ -298,7 +298,7 @@ class BertPreTrainingHeads(nn.Module):
         return prediction_scores, seq_relationship_score
 
 
-class BertPreTrainedModel(PretrainedModel): #(nn.Module):
+class BertPreTrainedModel(PreTrainedModel): #(nn.Module):
     """An abstract class to handle weights initialization and
     a simple interface for dowloading and loading pretrained models.
     """