fix deepseekv2 infra

Author: DrownFish19

paddlenlp/transformers/deepseek_v2/modeling.py

@@ -1746,7 +1746,6 @@ def prepare_inputs_for_generation(
     ):
         batch_size, seq_length = input_ids.shape
         position_ids = kwargs.get("position_ids", paddle.arange(seq_length).expand((batch_size, seq_length)))
-        attention_mask = kwargs.get("attention_mask", None)
         if past_key_values:
             input_ids = input_ids[:, -1].unsqueeze(axis=-1)
             position_ids = position_ids[:, -1].unsqueeze(-1)