Slice shape issue on page /20_image_segmentation/Segmentation_3D.html

Hello ,

Thank you for your work. There is always a notebook for what I am looking for!

In this notebook : https://haesleinhuepf.github.io/BioImageAnalysisNotebooks/20_image_segmentation/Segmentation_3D.html
In the section intensity and background correction I think the slice should be
```python
a_slice = cle.create([resampled.shape[1], resampled.shape[2]])
```


With the example data the change is not obvious but with less cubic data I think it will crop part of the image