fdo#85776 swap increase and decrease indent in sidebar

Change-Id: I5f6dd2244adecd2dba7e03ff3f620bd4c7657d7b
Reviewed-on: https://gerrit.libreoffice.org/12396
Reviewed-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>
Tested-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>