Fix splicing error in esxml-listify

Example text case:
  (esxml-listify '((a ((href . "/path/to/somewhere")) "blah")))
evaluates to
  (ul nil
      (li nil a
          ((href . "/path/to/somewhere"))
          "blah"))
instead of
  (ul nil
      (li nil (a
               ((href . "/path/to/somewhere"))
               "blah")))
so it was splicing each element of the input list.