Fix to install torch and torchvision on 1_VAEs.ipynb

[neelsoumya]

Fix to install torch and torchvision on 1_VAEs.ipynb

I had to do the following in the notebook (running on github codespaces)

https://github.com/acceleratescience/diffusion-models/blob/main/notebooks/1_VAEs.ipynb

pip install torch torchvision