message: fix type in doc
diff: @@ -597,8 +597,8 @@ Note that cell widths are defined _per refinement level_, not per block.
  float[] cellWidth NULL array of each level's cell width
  - box3f[] block.bounds NULL [data] array of bounds for each AMR
  - block
  + box3i[] block.bounds NULL [data] array of grid sizes (in voxels)
  + for each AMR block
  int[] block.level NULL array of each block's refinement
  level
  