bug#33191: 26.1.50; remove remaining process input batching doc

[Charles A. Roelli]

> Date: Sun, 09 Dec 2018 14:47:54 +0200
> From: Eli Zaretskii <eliz@gnu.org>
>
> Thanks, but this removes too much, IMO.  The 500 bytes figure should
> go away, but we still send the string in chunks, albeit
> system-dependent ones, and we still allow output from processes to
> arrive between chunks.

True, but it seems like chunked sending is broken somehow: Bug#6149
(GNU/Linux) and Bug#32438 (macOS) both show this.  (There may be
similar problems on MS Windows; I have not tested.)  If we say that
sending is done in chunks, users might infer that there are no such
problems.  Maybe we can add that system-dependent problems may occur
for input longer than 1 kB.