rename terms Movie/Sound to Audio/Video

Change-Id: I3afc007cd4a9b5dca83145f9b03b1393b546358d
Reviewed-on: https://gerrit.libreoffice.org/12127
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>