minor fix

Author: andrey-churkin

tests/onnx/quantization/test_weights_compression.py

@@ -372,7 +372,7 @@ def get_sequential_matmul_model() -> onnx.ModelProto:
             weights_data = np.arange(0, 16).reshape(4, 4).astype(np.float32)
             weights_data[-1, -1] = main_value
             weights_data = weights_data.T
-            mb.add_matmul(x, shape=weights_data.shape, output=output if i == 4 else None, data=weights_data)
+            x = mb.add_matmul(x, shape=weights_data.shape, output=output if i == 4 else None, data=weights_data)
 
         return mb.build()