removal proposal: emacs26 and emacs27 (and -nox11 variants)

[Greg Troxel <gdt%lexort.com@localhost>]

emacs29 is the current version, and emacs28 is one-behind, which is
useful to let people decouple their update timelines.

I am ignoring emacs20 and emacs21 in this note.

We have many versions, and I think we have 26 and 27 merely because new
versions are added and old ones don't get removed.

I suggest that we should tend to keep the current and previous, among
modern emacs, but this is merely a comment in this email which is about
two versions.

I propose to delete emacs26 and emacs27, on the ground that they are old
and unmaintained, and likely either have no users or the people that are
could just switch to 28 or 29 with ~zero hassle.  And, that if we didn't
have lots of versions anyway, we might have just had one and that would
have been updated, like any normal package.

I'll set July 2 at 1200Z (an hour less than 7 days from now) as the
propoal timeline, because I think removal proposals should have a week
for comments.

If you are using emacs26 or emacs27, main or -nox11, and if migrating to
28 or 29 is trouble, please speak up and explain.  (If you are using 26
or 27 because you simply have never tried newer, please try newer now.)

Greg