Stop logging with the GettingStartedOnRedirect schema.

Logging events with the GettingStartedOnRedirect schema is no longer
required.

* Remove the mw.gettingStarted.logging, .logUnlessTimeout, and
  .logImpression methods and their uses
* Stop loading the GettingStartedOnRedirect schema
* Remove the redundant ext.gettingstarted.openTask module

Change-Id: If814a147dec19a8f2222f4e3154a3f800d108dc2