Prevent duplicate torch_dtype kwargs (#115)

Throws an error currently if you specify a `torch_dtype` in the `model_config`.

```pycon
TypeError: transformers.models.auto.auto_factory._BaseAutoModelClass.from_pretrained() got multiple values for keyword argument 'torch_dtype'
```

llmlingua/prompt_compressor.py

@@ -138,7 +138,7 @@ def load_model(
         if "cuda" in device_map or "cpu" in device_map:
             model = MODEL_CLASS.from_pretrained(
                 model_name,
-                torch_dtype=model_config.get(
+                torch_dtype=model_config.pop(
                     "torch_dtype", "auto" if device_map == "cuda" else torch.float32
                 ),
                 device_map=device_map,
@@ -150,7 +150,7 @@ def load_model(
             model = MODEL_CLASS.from_pretrained(
                 model_name,
                 device_map=device_map,
-                torch_dtype=model_config.get("torch_dtype", "auto"),
+                torch_dtype=model_config.pop("torch_dtype", "auto"),
                 pad_token_id=tokenizer.pad_token_id,
                 **model_config,
             )