nestedtensor.py on Colab building from master

[alex-rakowski]

When running the nested tensors tutorial on google colab builds from master instead of main. The master branch version is non-functional, main branch version appears to work correctly:

• nested tensors created with torch.nested_tensor instead of torch.nested.nested_tensor
• the mha_netsed function handle batch size inference incorrectly.

[alex-rakowski]

The webpage also appears to be building from master, it seems like the SPHINX-GALLERY maybe the tutorials page/s is/are building from master instead of main

[svekars]

This tutorial is currently disabled as the current version does not work with PyTorch 1.13. It will be enabled and functional for PyTorch 2.0.