bug#39546: 28.0.50; Do not require subr-x at run time

[Tino Calancha]

On Mon, 10 Feb 2020, Eli Zaretskii wrote:

> > In addition, it moves back replace-region-contents into subr.el: been a defun,
> > and documented in the manual, then it fits better inside subr.el.
>
> subr.el is preloaded, so doing that will enlarge the Emacs memory
> footprint.  Is that function important enough to have it preloaded?
According with its usage at Emacs source (only at json.el) I'd say
the answer to your question is: not worth to be at subr.el.