Editorial: fix typo in li element guidance (#515)

Previous: "... if the parent list item does not ...."

Corrected text: "... if the parent list element does not ..."

index.html

@@ -2257,7 +2257,7 @@ <h2 id="docconformance">
                   if the parent list element has an implicit or explicit `list` role.
                 </p>
                 <p>
-                  Otherwise, <a><strong>any `role`</strong></a> if the parent list item does not expose an implicit or explicit `list` role.
+                  Otherwise, <a><strong>any `role`</strong></a> if the parent list element does not expose an implicit or explicit `list` role.
                 </p>
                 <p class="note">
                   See <a href="#el-ul">`ul`</a>, <a href="#el-ol">`ol`</a>, or