BUG: Fix the ITK clone URL.
BUG: Fix the ITK clone URL.

This is a follow-up to
KitwareMedical/TubeTK@2b3fe664eee25653dc0c391feae95ff87079d768

The github.com/Slicer/ITK.git repository does not have a copy of the ITK
master branch and the commit is missing.

This causes the build failure:

Error
  CMake Error at Stamp/ITK/ITK-download-Release.cmake:16 (message):
    Command failed: 1

     'C:/Program Files (x86)/CMake/bin/cmake.exe' '-P' '/.../TubeTK-Release/tmp/ITK/ITK-gitclone.cmake'

    See also

      /.../TubeTK-Release/Stamp/ITK/ITK-download-*.log

cdeepakroy/TubeTK,sumedhasingla/TubeTK,KitwareMedical/TubeTK,KitwareMedical/TubeTK,aylward/ITKTubeTK,cdeepakroy/TubeTK,thewtex/TubeTK,KitwareMedical/ITKTubeTK,aylward/ITKTubeTK,aylward/ITKTubeTK,sumedhasingla/TubeTK,KitwareMedical/TubeTK,sumedhasingla/TubeTK,cdeepakroy/TubeTK,aylward/ITKTubeTK,thewtex/TubeTK,KitwareMedical/ITKTubeTK,thewtex/TubeTK,KitwareMedical/ITKTubeTK,sumedhasingla/TubeTK,cdeepakroy/TubeTK,KitwareMedical/TubeTK,thewtex/TubeTK,KitwareMedical/ITKTubeTK