Remove duplicated class vtkmOutputFilterPolicy
Occurrences:
This was discovered while working on !8885 (merged).
It is important to avoid duplicated symbol names to avoid violating the ODR (One Definition Rule).
For some more context, see https://discourse.slicer.org/t/transition-of-nightly-build-from-vtk-9-0-20201111-to-9-1-20220125/21669/
Edited by Jean-Christophe Fillion-Robin