lstopo/graphics: fix/reduce the width of OS device boxes
lstopo/graphics: fix/reduce the width of OS device boxes

Don't add gridsize again to textwidth, it's already in textwidth.

(broken when uniformizing things in commit 307d78dfb9e5a371363efdac5674429af7ab6e93)

shekkbuilder/hwloc,shekkbuilder/hwloc,shekkbuilder/hwloc,shekkbuilder/hwloc