Fixing BinaryDilate cells in 300_Segmentation_Overview notebook

[kolibril13]

I think two cells with BinaryDilate in
https://github.com/InsightSoftwareConsortium/SimpleITK-Notebooks/blob/master/Python/300_Segmentation_Overview.ipynb
should be rewritten to this way:
https://simpleitk.readthedocs.io/en/master/migrationGuide2.0.html?highlight=BinaryDilate#morphology-radius