Make protected setter method public

Setter method should probably have originally been public but
was instead protected. Changing it to public now.
Status Job ID Name Coverage
  External
passed cdash-buildbot

passed ghostflow-branch-check-master

failed vtk@master-adora-linux-shared-release+cuda+gcc+mpi+optix+python2+tbb+vtkm

00:35:16

passed vtk@master-bigmac-osx-shared-debug+adios2+clang+python2+vtkm

00:26:15

failed vtk@master-duma-linux-shared-release+osmesa+ospray

00:28:13

running vtk@master-eeloo-linux-shared-release+adios2+extdeps+java+mpi+python3+qt+tbb+vtkm

4554:54:16

running vtk@master-eeloo-linux-shared-release+mpi+nogl

4554:54:16

failed vtk@master-luigi-linux-shared-release+mpi+python2+tbb

00:38:09

failed vtk@master-mun-windows-shared-release+kits+mpi+python3+qt+tbb

00:53:55

failed vtk@master-mun-windows-shared-release+mpi+python3+tbb+vtkm

00:22:52

failed vtk@master-mun-windows-static-release+mpi+qt+tbb

00:54:22

failed vtk@master-taanab-linux-shared-release+adios2+mpi+python2

00:21:23

passed vtk@master-trey-osx-shared-release+python3+qt

00:55:59