Enable flash_attention_2 support since the underlying Mistral model supports it

modeling_eurus_rm.py

@@ -5,6 +5,8 @@ from typing import Optional, List
 
 class EurusRewardModel(PreTrainedModel):
     config_class = MistralConfig
+    _supports_flash_attn_2 = True
+
     def __init__(self, config):
         super().__init__(config)
         self.model = MistralModel(config)