Remove "extract_slice.py", obsoleted by "make_lightcone.py"
Remove "extract_slice.py", obsoleted by "make_lightcone.py"

liweitianux/atoolbox,liweitianux/atoolbox,liweitianux/atoolbox,liweitianux/atoolbox,liweitianux/atoolbox,liweitianux/atoolbox