transport-next-link: Rename a variable for clarity

Make it more obvious that this variable corresponds to the original
link's description, not the new description specified by the word at
point or the selected text.

org-link-edit.el

@@ -374,9 +374,9 @@ END."
                      (org-link-edit--on-link-p)))
       (user-error "Cannot transport next link with point on a link"))
     (goto-char (or (car desc-bounds) pt))
-    (cl-multiple-value-bind (link-beg link-end link desc)
+    (cl-multiple-value-bind (link-beg link-end link orig-desc)
         (org-link-edit--next-link-data previous)
-      (unless (or (not desc-bounds) (= (length desc) 0))
+      (unless (or (not desc-bounds) (= (length orig-desc) 0))
         (user-error "Link already has a description"))
       (delete-region link-beg link-end)
       (insert (org-make-link-string