Client return type error

[hilak]

https://github.com/kaltura/server/blob/bf3506730020bc8e85ab5ed0a94ef3d62f03fe99/plugins/content/caption/base/services/CaptionAssetService.php#L819

Since KalturaCaptionAsset is not an inheritor of KalturaFlavorAsset but of KalturaAsset - this return type causes generated client libraries to throw an error on the return type. It's not a major issue since the export still takes place, but still worth fixing.