No more "Prefix Command" in C-h m

[Bob Rogers]

   A while ago, I noticed that C-h m no longer shows keys bound to
keymaps as "Prefix Command" along with their siblings when I almost
clobbered such a prefix when looking for an unused key sequence.  I was
about to submit a bug report when I noticed the comment in the code that
said this was a design choice.  The commit was a5d79fcfe83e by Lars
Ingebrigtsen on 2021-11-01.  Lars, would you please tell us why?

                                        -- Bob Rogers
                                           http://www.rgrjr.com/