Fix spleen_segmentation_3d_visualization_basic (#1147)

Fixes #1139 .

### Description
- Fix bug in validation
- Add text to remind opening port 53800 for using AIM UI in notebook
- Add license and rearrange cells to follow contributing guidelines

### Checks
<!--- Put an `x` in all the boxes that apply, and remove the not
applicable items -->
- [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
"3d_segmentation/spleen_segmentation_3d_visualization_basic.ipynb"`

Signed-off-by: Mingxin Zheng <18563433+mingxin-zheng@users.noreply.github.com>

Author: mingxin-zheng