Currently, fzf's cd widget executes the cd command via accept-line, so
the command is also visible in the scrollback buffer. In contrast to
this, the cd-{forward,backward,up} suite changes the directory in-place,
without touching BUFFER, with an additional prompt redraw (one could say
"in-prompt"). Since I find this more appealing, overwrite the default
fzf widget with a custom one that has the same behaviour.