Update customize-package-emacs-version-alist

Update customize-package-emacs-version-alist

* lisp/org.el (customize-package-emacs-version-alist): Add entries for
all existing ":package-version" values, and remove entries for
versions that aren't used as ":package-version" values.

Note that this alist has a limited effect because we specify
":version" in almost all of our defcustoms.  Two functions make use of
this alist: describe-variable-custom-version-info and
customize-changed-options.  The former only looks at the alist if
:version isn't specified, and the latter only looks at :version if an
entry for :package-version isn't found in the alist.

We should consider removing the defcustom :version specifications so
that the package-version->version mapping only needs to be maintained
in one place.