Parameters: evaluate_hetvae

In [synthetic_data_interpolation.ipynb](https://github.com/reml-lab/hetvae/blob/main/src/synthetic_data_interpolation.ipynb), the function **evaluate_hetvae** (from [utils](https://github.com/reml-lab/hetvae/blob/main/src/utils.py)) has an extra parameter `model_name`, but this parameter isn't defined. If you ignore `model_name` parameter, the jupyter notebook works out.