bug#57434: 28.1.91; Terminal Emacs Mac OS flickering.

[Eli Zaretskii]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: Dmitrii Kuragin <kuragin@google.com>,  57434@debbugs.gnu.org
> Date: Wed, 21 Sep 2022 08:10:02 +0200
> 
> Plus something had to be changed with regard to fflush at the end of
> the update (it was called too early, or too late).

Too late.  We should call it before the call to update_end.