Cleanup: Remove unused 'DispOp' enum

Pull Request: https://projects.blender.org/blender/blender/pulls/145289

source/blender/blenkernel/intern/multires.cc

@@ -48,13 +48,6 @@ static const int multires_grid_tot[] = {
 static const int multires_side_tot[] = {
     0, 2, 3, 5, 9, 17, 33, 65, 129, 257, 513, 1025, 2049, 4097};
 
-/* See multiresModifier_disp_run for description of each operation */
-enum DispOp {
-  APPLY_DISPLACEMENTS,
-  CALC_DISPLACEMENTS,
-  ADD_DISPLACEMENTS,
-};
-
 /** Custom-data. */
 
 void multires_customdata_delete(Mesh *mesh)