This fixes a regression introduced in
8aeccc6240 whereby packages specified via
-e, -r, or -m, as well as packages *not* specified on the command line,
would all lead to a wrong-type error.
Reported by Ricardo Wurmus <rekado@elephly.net> at
<https://lists.gnu.org/archive/html/guix-devel/2022-12/msg00311.html>.
* guix/scripts/refresh.scm (<update-spec>): Move above. Rename
constructor to '%update-spec' and add separate 'update-spec' procedure
with optional #:version parameter.
(options->update-specs): Always return a list of <update-spec> and
update docstring accordingly. Rename 'args-packages' to 'update-specs'
and ensure it's a list of <update-spec>; handle 'manifest' arguments
here.