fdo#85907 Better use of space in Special Characters dialog

Change-Id: Iaa42e8ef7727291ba112fc92db5051951046f86f
Reviewed-on: https://gerrit.libreoffice.org/12265
Reviewed-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>
Tested-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>