bug#53636: 29.0.50; face-remapping broken on master

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: 53636@debbugs.gnu.org,  tsdh@gnu.org
> Date: Sun, 13 Feb 2022 09:20:24 +0100
> 
> I guess we should just document that face remapping doesn't work
> reliably when remapping parent faces to the basic faces?

Yes, I think so.

> And for this bug report, the answer is "you have to use mode-line-active
> instead of mode-line".

Right.