maint: Remove core/remove and core/url.

Remove core/remove and core/url and it's usage in pat-slides. core/url
wasn't used at all and core/remove did invoke the event to invoke
clean-up routines.

But core/remove did that by patching the internal cleanData jQuery API.
This resulted in an infinite recursion error in combination with
pat-tiptap from Mockup.

pat-slides is currently not in a working state, so the removal is OK.
Anyways, this triggers the question how to handle Pattern cleanup in the
future. The answer is in a mutation observer on document level, but this
will be part of a future release.

Author: thet

src/core/remove.js

@@ -6,8 +6,6 @@
 import $ from "jquery";
 import registry from "../../core/registry";
 import utils from "../../core/utils";
-import url from "../../core/url";
-import "../../core/remove";
 
 var slides = {
     name: "slides",