mw.ViewPageTarget: Remove obsolete transitions for margin
These were there to match Vector, however as of 4cec8a70589
Vector no longer has these. Having these in VisualEditor causes
the toolbar to be a few pixels behind (like a slingshot) when the
rest of the skin has already moved.
Change-Id: Ia5886a58316ccb3b0420553c3f466b5256089c73