Remove duplicate lines from test CMakeLists
Remove duplicate lines from test CMakeLists

It appears that these four lines are exact copies of the four lines
above. Here's the values in PDAL_UNITTEST_SOURCES for my build:
https://gist.github.com/gadomski/5918454. The files in lines 1-51 of the
gist are duplicated in lines 52-102.

DougFirErickson/PDAL,DougFirErickson/PDAL,jwomeara/PDAL,radiantbluetechnologies/PDAL,radiantbluetechnologies/PDAL,boundlessgeo/PDAL,lucadelu/PDAL,lucadelu/PDAL,mtCarto/PDAL,jwomeara/PDAL,Sciumo/PDAL,mpgerlek/PDAL-old,verma/PDAL,lucadelu/PDAL,mtCarto/PDAL,lucadelu/PDAL,verma/PDAL,verma/PDAL,Sciumo/PDAL,mpgerlek/PDAL-old,mtCarto/PDAL,jwomeara/PDAL,DougFirErickson/PDAL,Sciumo/PDAL,mpgerlek/PDAL-old,radiantbluetechnologies/PDAL,mtCarto/PDAL,mpgerlek/PDAL-old,boundlessgeo/PDAL,Sciumo/PDAL,verma/PDAL,verma/PDAL,boundlessgeo/PDAL,jwomeara/PDAL,DougFirErickson/PDAL,radiantbluetechnologies/PDAL,boundlessgeo/PDAL,verma/PDAL,verma/PDAL