Update CMakeLists.txt

I met the following error when I try to build paraview on my Ubuntu 18.04 64bit system.

CMake Error at VTK/CMake/vtkModule.cmake:2862 (add_library):
  Cannot find source file:

    FortranPythonAdaptorAPI.cxx.cxx

  Tried extensions .c .C .c++ .cc .cpp .cxx .m .M .mm .h .hh .h++ .hm .hpp
  .hxx .in .txx
Call Stack (most recent call first):
  CoProcessing/PythonCatalyst/CMakeLists.txt:52 (vtk_module_add_module)


CMake Error: CMake can not determine linker language for target: PythonCatalyst
CMake Error in CoProcessing/PythonCatalyst/CMakeLists.txt:
  Exporting the target "PythonCatalyst" is not allowed since its linker
  language cannot be determined

The 47 line of CoProcessing/PythonCatalyst/CMakeLists.txt

FortranPythonAdaptorAPI.cxx)

should be

ForFortranPythonAdaptorAPI)