I've tried hitting the minus button next to a resource, which hides it, but when I press "update" then refresh the page, the jsfiddle still contains the resource that I thought I removed.
(Maybe there's a bug in jsfiddle?)
For example, try forking https://jsfiddle.net/trusktr/32cnvse3, then try to remove any of the "external resources".
Asa workaround, I made a new fiddle then copied over all the code and added the desired external resources: https://jsfiddle.net/trusktr/apnax8va, but that means I have to go and update all previous URLs to point to the new fiddle.
// blah (ignore this)
Apparently it's been fixed. It works now.