Fix failure to override num_epochs for auto3dseg HPO demo

Partly fixes #1679 for HPO, and limit the models for HPO demo.

A few sentences describing the changes proposed in this pull request.

[x] Avoid including large-size files in the PR.
[x] Clean up long text outputs from code cells in the notebook.
[x] For security purposes, please check the contents and remove any sensitive info such as user names and private key.
[x] Ensure (1) hyperlinks and markdown anchors are working (2) use relative paths for tutorial repo files (3) put figure and graphs in the ./figure folder
[x] Notebook runs automatically ./runner.sh -t <path to .ipynb file>

Project-MONAI / tutorials