bug#51210: Customizable other-window-for-scrolling

[Juri Linkov]

> If you must change it, please introduce a user option, by default
> off.

An option could be added indeed, but wasn't 'recenter' intended
only to refresh the screen, not to recenter?

'beginning-of-buffer-other-window' has such line at the end:

  (recenter '(t))

Clearly it makes no sense to recenter at the beginning of the buffer.
So the value '(t)' was intended only to refresh the screen?
Then the same line in 'end-of-buffer-other-window'
should only refresh the screen, not recenter.