skip the re-registration scan in SwTableBox::ChgFrameFormat, which we
don't need since we are creating this table for the first time

On my machine,
loading the  69 page file goes from 40.9s to 30.4s
loading the 128 page file goes from 79.1s to 45.1s

Change-Id: Id9e48256556e19eca34a892b29beff7eab9f51f1
Reviewed-on: https://gerrit.libreoffice.org/69885Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Noel Grandin <noel.grandin@collabora.co.uk>