Improve behat performance by jumping straight to editing on mode

We have a step:

And I am on "Course 1" course homepage with editing mode on

At the moment this step is crazy slow because it opens the page
Looks for one type of course editing menu (for Classic)
Fails to find it and then looks for the Boost one
Opens the dropdown
Presses Turn editing on

The way in which we use this step means that we don't really need to prove this works because we do so in specific steps.
We can just jump straight to the correct URL.

We do need to look up the sesskey from the current session (a little bit icky but not too bad) and that's it.