bug#35290: 27.0.50; Outdated vc-revert documentation

[Eli Zaretskii <eliz@gnu.org>]

> From: Mauro Aranda <maurooaranda@gmail.com>
> Date: Mon, 15 Apr 2019 12:54:45 -0300
> 
> 1) C-h r
> 2) m VC Undo
> 
> Read this sentence:
> Note that ‘C-x v u’ cannot be reversed with the usual undo commands
> (see Undo), so use it with care.
> 
> To check it is outdated:
> 1) emacs -Q
> 2) C-x C-f FILE-UNDER-VERSION-CONTROL
> 3) Make some changes and then C-x C-s
> 4) Revert: C-x v u
> 5) Confirm: yes RET
> 6) After reverting is done, type C-/
> 7) Observe that you got your changes back.

I believe this is a misunderstanding due to the inherent ambiguity of
"undo" in this context.  The text wants to say that you cannot undo
the effect in the repository, not in the buffer that visits the file.

Thanks.