As a hold-over from a previous porting attempt, thw World.js file
(a cucumber.js convention) exported an instance of MWBot. This
instance was used in several tests, however, since MWBot had been
instantiated multiple times since then, the original edit token
was invalid, causing several tests to fail.
Bug: T224947
Change-Id: I56c06600c43d53bbc4e103d446a1de7a52c2cfad