bug#3303: delete-frame raises old (invisible) frame

[Stefan Monnier]

> The symptom I observed that led me to add that section of code was that,
> when two frames are open, both displaying different buffers,  and you hold
> the cursor-down or page-down key down in one, the focus  would shift back
> and forth between the windows, and the cursor would  do some movement in
> each.  It's possible this no longer occurs due to  other changes in focus
> handling both on NS and core sides, but it's  worth testing.

Then it's good to remove the workaround, even if the symptom re-appears:
it should be fixed elsewhere.


        Stefan