bug#31536: Misused Texinfo markup in misc.texi and ack.texi(emacs-26).

[Takesi Ayanokoji]

Hi Emacs developers.

In misc.texi (and ack.texi), there are misused Texinfo markups.

>>> start here

ack.texi:1099:William Schelter wrote @file{telnet.el}, support for @code{telnet}

misc.texi:1513:would from a regular terminal (e.g., using the @code{ssh} or

misc.texi:1514:@code{telnet} or @code{rlogin} commands), from a Term window.

<<<end here

I think these @code{...} markups should marked with @command{...}.

Thanks.

ayatakesi <ayanokoji.takesi@gmail.com>