vi-mode.fish: Fix replace mode by removing old workaround
vi-mode.fish: Fix replace mode by removing old workaround

Originally I had to put a hack in replace mode to make it work,
presumably to work around a bug in fish. This no longer works in fish
2.1.0 because presumably the bug was fixed, so remove the workaround and
use the correct procedure.

DarkStarSword/junk,DarkStarSword/junk,DarkStarSword/junk,DarkStarSword/junk,DarkStarSword/junk