fdo#75673 - Removed duplicate insert entries

Inserting audio and video was duplicated in media and object
menus. Removed from object to match every other component.

Change-Id: I221e73184b835554c8c6a9293a8042a24d429030
Reviewed-on: https://gerrit.libreoffice.org/12276
Reviewed-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>
Tested-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>