related fdo#70998 use plural for Objects/Images option

Change-Id: Ia76021bcb9044a10b880c12fcbf67e86b837ebd4
Reviewed-on: https://gerrit.libreoffice.org/11811
Reviewed-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>
Tested-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>