docs(group) remove reference to lv_cont which is gone in v8
As reported on the forum:
@@ -53,7 +53,7 @@ typedef void (*lv_group_focus_cb_t)(struct _lv_group_t *);
/**
* Groups can be used to logically hold objects so that they can be individually focused.
- * They are NOT for laying out objects on a screen (try `lv_cont` for that).
+ * They are NOT for laying out objects on a screen (try layouts for that).
*/
typedef struct _lv_group_t {
lv_ll_t obj_ll; /**< Linked list to store the objects in the group*/
