they are really png in icon-themese and while some fallback
code will find the png if they get included in the final zips
the zip builder won't include them if the name doesn't match

Change-Id: I0f08685403f8e4a92b7661edcbb8b14af1034fea
Reviewed-on: https://gerrit.libreoffice.org/40728Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>