bug#49193: Document require-final-newline vs. readonly files

[Eli Zaretskii]

> From: 積丹尼 Dan Jacobson <jidanni@jidanni.org>
> Cc: 49193@debbugs.gnu.org
> Date: Thu, 24 Jun 2021 03:22:22 +0800
> 
> EZ> There's nothing to mention, because this feature doesn't change how
> EZ> saving to an unwritable file behaves in Emacs.  The feature works on
> EZ> the buffer text, not on the buffer's file.
> 
> Ah, that clears things up.
> So please mention that.

I don't see a reason to mention that feature A doesn't change how
feature B works, for every combination of A and B.

So I'm closing this bug report.