Fix shuffle error in 2d_slices_from_3d_sampling.ipynb (Project-MONA…

…I#1577)

Fix Project-MONAI#1576

The error was introduced by
Project-MONAI/MONAI#7180.

### Checks
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applicable items -->
- [ ] Avoid including large-size files in the PR.
- [ ] Clean up long text outputs from code cells in the notebook.
- [ ] For security purposes, please check the contents and remove any
sensitive info such as user names and private key.
- [ ] 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
- [ ] Notebook runs automatically `./runner.sh -t <path to .ipynb file>`

Signed-off-by: KumoLiu <yunl@nvidia.com>