test: Remove obsolete fix for OO#compare

This bug has been fixed in OOjs for a while now.
test: Update to work with latest version

* Remove veaction=edit so that we can set the cookie for welcome
  dialog in time before the editor loads.
* Update property names and methods according to version of
  VisualEditor currently in use at en.wikipedia.org.

Screencapture may no longer cover the part that's offscreen.