Remove a GtkFrame and its redundant label

It’s more than obvious that these are “Options”.

Change-Id: I192a1864bc43b3e20e98e179282dac02abbdbbf4
Reviewed-on: https://gerrit.libreoffice.org/11925
Reviewed-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>
Tested-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>