Remove ITK-4.8 Python path directory.
Remove ITK-4.8 Python path directory.

For ITK 4.9.0, this path addition should not be required because ITK now uses
a more standard installation location.

This has removed all ITK-4.8 references in the tomviz repository (as verified
with git grep).

cryos/tomviz,cryos/tomviz,mathturtle/tomviz,mathturtle/tomviz,thewtex/tomviz,OpenChemistry/tomviz,cjh1/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,mathturtle/tomviz,cjh1/tomviz,OpenChemistry/tomviz,cjh1/tomviz,thewtex/tomviz,thewtex/tomviz,cryos/tomviz