Fix scrollability of the preview window in certain cases
Fix scrollability of the preview window in certain cases

Fix #2683

This commit fixes the cases where fzf incorrectly determines the
scrollability of the preview window when `--preview-window-wrap` is set.

Wrapping of the preview content happens during the rendering phase, so
it's currently not possible to know how many lines are actually needed
to display the content beforehand. So `preview-bottom` still may not
move to the very bottom with wrapping enabled.

junegunn/fzf,junegunn/fzf,junegunn/fzf