Fix fdo#84574 - COLOR PICKER: Palette color list should have scrollbar

Change-Id: Ib927d3e1b1349f9a1b5f575180d217fe31f1f11f
Reviewed-on: https://gerrit.libreoffice.org/12296
Reviewed-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>
Tested-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>