Original PR description

### Issue:
When trying to upload the video for a Youtube post, we are getting a traceback with "UncaughtPromiseError > TypeError", caused by not having the `youtube_video_category_id` field properly loaded, at the time where we are trying to evaluate `_preprocessReferenceChanges` we try to access the type of the field as `this.fields[fieldName].type === "reference"` where `fieldName` is `youtube_video_category_id`, but the field is not loaded yet (this.fields[fieldName] is undefined), so we get an error.

### Solution:
This commit adds this field as a field dependecy for the `YoutubeUploadField`  widget, so that it is loaded when we try to access it.

opw-4646432