Deleting failing test updateDirectlyWithHtml.

loadJSON does not support parsing HTML.
Nor should it need to, since UC URLs are supposed to be to the JSONP file.
The .html extension is added automatically by downloadService when postBack is supported.
(cherry picked from commit d6b37a94)

Conflicts:
	test/src/test/java/hudson/model/UpdateSiteTest.java
	test/src/test/resources/hudson/model/update-center.json.html