bug#47236: 28.0.50; ebdb-mua-pop-up bad interaction with gnus window configurations

[Eli Zaretskii]

> From: Robert Pluim <rpluim@gmail.com>
> Date: Tue, 29 Jun 2021 09:44:58 +0200
> Cc: 47236@debbugs.gnu.org
> 
> Idle thought: maybe we should just remove mail-mode and add some
> compatibility code pointing at message.

Please don't.  I'm a heavy user of mail-mode, and I hate message-mode
(because everything there is slightly off-course from my POV).