Only allow delta updates to avoid exposing app URL in appcast.xml

[nickasd]

Would it be a good idea to add an option to only allow downloading delta updates to avoid exposing the app URL?

Someone already asked this on Reddit, and someone suggested removing the <enclosure> tag, but doing so produces a Console error Error: No enclosure in feed item (null) (URL (null)).

[nickasd]

Found #2465.