Re-add assert to fix deadlock

For some reason, `UnitTestContourTreeUniformAugmentedFilterCUDA` was
deadlocking on some of the dashboards when `VTKM_ASSERT` was changed to
be empty when compiling CUDA kernels (for compiler performance reasons).
Fix this by calling `assert` directly in this case.

For the life of me, I cannot figure out why this would be an issue.
Clearly the `assert` is never actually called or else the test would
error out (unless a special condition in CUDA is causing it to be
hidden). But if you take out the code, something changes to lock up the
kernel.

vtkm/worklet/contourtree_augmented/mesh_dem_meshtypes/MeshStructureMarchingCubes.h

@@ -227,7 +227,7 @@ public:
         return SortIndicesPortal.Get(meshIndex + (this->NumRows * this->NumColumns) +
                                      this->NumColumns + 1); // {  1,  1,  1 }
       default:
-        VTKM_ASSERT(false);
+        assert(false);
         return meshIndex; // Need to error out here
     }
   } // GetNeighbourIndex