fdo#75256 Improve Sifr Icontheme

Update sc_inserttable, because the vertical lines are not in the pixelgrid and are blurried.

Change-Id: Ieb5723396e6a6c4300ad205fe0c0c646167ee01b
Reviewed-on: https://gerrit.libreoffice.org/12235
Reviewed-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>
Tested-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>