fix: remove `StableLMEpochForCausalLM.transformer` refs

modeling_stablelm_epoch.py

@@ -561,10 +561,10 @@ class StableLMEpochForCausalLM(StableLMEpochPreTrainedModel):
         self.lm_head = new_embeddings
 
     def get_decoder(self):
-        return self.transformer
+        return self.model
 
     def set_decoder(self, decoder):
-        self.transformer = decoder
+        self.model = decoder
 
     def forward(
         self,