Update office-365-cdn.md

Removing section indicating Content By Search web parts support private CDN for image assets.  Per response on https://icm.ad.msft.net/imp/v3/incidents/details/89072799/home and subsequent email discussion, this is not actually supported yet and no ETA has been provided on when it will be.  Removing documentation that it is to avoid further customer confusion.

Author: tieven

docs/general-development/office-365-cdn.md

@@ -68,9 +68,6 @@ The following is an overview of which links are automatically rewritten by the S
   - When extending pages, you can temporarily disable auto-rewriting URLs on a page by:
     - checking out the page
     - providing the query string parameter `?NoAutoReWrites=true`
-- Content By Search WebPart assets
-  - Display template JavaScript files
-  - Images in query results - URLs in the following standard Managed Properties are automatically replaced: _PictureUrl_, _PictureThumbnailUrl_, _PublishingImage_
 - Picture Library SlideShow webpart image URLs
 - Image fields in SPList REST API (RenderListDataAsStream) results
   - Use the new property ImageFieldsToTryRewriteToCdnUrls to provide a comma separated list of Fields.