Fix splicing error in esxml-listify

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