Fix the ORTQuantizer model path of the model to quantize (#701)

Fix ort quantizer loading from specific file

optimum/onnxruntime/quantization.py

@@ -134,7 +134,7 @@ def from_pretrained(
 
         if isinstance(model_or_path, ORTModelForConditionalGeneration):
             raise ValueError(ort_quantizer_error_message)
-        elif isinstance(model_or_path, Path):
+        elif isinstance(model_or_path, Path) and file_name is None:
             onnx_files = list(model_or_path.glob("*.onnx"))
             if len(onnx_files) == 0:
                 raise FileNotFoundError(f"Could not find any ONNX model file in {model_or_path}")