message: fix a bug in one of the ava properties.
diff: "VideoPublishingOptions": {
  "type": "object",
  "properties": {
  - "enableVideoPreviewImages": {
  + "enableVideoPreviewImage": {
  "type": "string",
  "description": "When set to 'true' the video will publish preview images. Default is 'false'."
  }
  