Remove trailing whitespace from license text

lib/spack/spack/package.py

lib/spack/spack/packages/__init__.py

lib/spack/spack/packages/callpath.py

lib/spack/spack/packages/cmake.py

lib/spack/spack/packages/dyninst.py

lib/spack/spack/packages/libdwarf.py

lib/spack/spack/packages/libelf.py

lib/spack/spack/packages/libunwind.py

lib/spack/spack/packages/mpich.py

lib/spack/spack/packages/mpileaks.py

lib/spack/spack/parse.py

lib/spack/spack/relations.py

lib/spack/spack/spec.py

lib/spack/spack/stage.py

lib/spack/spack/test/__init__.py

lib/spack/spack/test/concretize.py

lib/spack/spack/test/mock_packages/__init__.py

lib/spack/spack/test/mock_packages/callpath.py

lib/spack/spack/test/mock_packages/direct_mpich.py

lib/spack/spack/test/mock_packages/dyninst.py