oc-csl: Small refactoring

* lisp/oc.el (org-cite-wrap-citation): Mention return value.
* lisp/oc-csl.el (org-cite-csl--create-structure): Use return value
from `org-cite-wrap-citation' instead of using `org-element-lineage'.

lisp/oc-csl.el

@@ -501,8 +501,7 @@ INFO is the export state, as a property list."
     ;; a footnote, but isn't yet.
     (when (and (not footnote) (org-cite-csl--note-style-p info))
       (org-cite-adjust-note citation info)
-      (org-cite-wrap-citation citation info)
-      (setq footnote (org-element-lineage citation '(footnote-reference))))
+      (setq footnote (org-cite-wrap-citation citation info)))
     ;; Return structure.
     (apply #'citeproc-citation-create
            `(:note-index

lisp/oc.el

@@ -872,7 +872,9 @@ When non-nil, the return value if the footnote container."
 INFO is the export state, as a property list.
 
 White space before the citation, if any, are removed.  The parse tree is
-modified by side-effect."
+modified by side-effect.
+
+Return newly created footnote object."
   (let ((footnote
          (list 'footnote-reference
                (list :label nil