fixed typo

include/ll.h

@@ -90,7 +90,7 @@ char *ll_get(ll_map_t *dict, char *key);
 
 /**
  * Returns an array of all the keys in the dict. The array should
- * be freed with `strarray_free` when it is no longer needed. See `str_util.h` 
+ * be freed with `strarray_free` when it is no longer needed. See `strarray.h` 
  * for more information on `strarray_t`.
  */
 strarray_t *ll_get_keys(ll_map_t *dict);