do not show progress bar for python notebook, as it will crash

[mitchdz]

This is currently blocking CI.

you will see:

nbclient.exceptions.CellExecutionError: An error occurred while executing the following cell:
------------------
discrete_pipeline = DiffusionPipeline.from_pretrained(
            repo_id="Floki00/qc_unitary_3qubit", # Download model from Hugging Face
            device=device)

in the validation stage - https://github.com/NVIDIA/cuda-quantum/actions/runs/18463430855/job/52615014928?pr=3502#step:7:968

This is because the progress bar crashes inside nbconvert, since it tries to look for a frontend which doesn't exist. This sets an environment variable to disable that progress bar (Which isn't shown anyways).

[github-actions]

CUDA Quantum Docs Bot: A preview of the documentation can be found here.

[github-actions]

CUDA Quantum Docs Bot: A preview of the documentation can be found here.

[1tnguyen]

👍