message: [XLA GPU] [NFC] Make it obvious that num_threads_y is always 1 for reduction
diff: @@ -2913,7 +2913,6 @@ ReductionCodegenInfo IrEmitterUnnested::ComputeReductionCodegenInfo(
  int64 tile_size_y = 1;
  int64 block_size_z = 1;
  int64 num_threads_x = 1;
  - int64 num_threads_y = 1;
  bool dilated_x = true;
  if (reduction_dimensions.is_row_reduction) {
  num_threads_x = kWarpSize;
  @@ -2958,9 +2957,9 @@ ReductionCodegenInfo IrEmitterUnnested::ComputeReductionCodegenInfo(
  tile_size_y = 128;
  }
  - KernelMappingScheme mapping_scheme(reduction_dimensions.dimensions,
  - tile_size_y, tile_size_x, block_size_z,
  - num_threads_y, num_threads_x, dilated_x);
  + KernelMappingScheme mapping_scheme(
  + reduction_dimensions.dimensions, tile_size_y, tile_size_x, block_size_z,
  + /*num_threads_y=*/1, num_threads_x, dilated_x);
  return ReductionCodegenInfo(mapping_scheme,
  reduction_dimensions.is_row_reduction);
  }
  