Remove the note regarding `waste_size` from `tuple_object.info()`

[TarantoolBot]

Product: Tarantool
Root document: https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_tuple/info/#box-tuple-info

Remove the following note: waste_size is provided for reference only and
can be inaccurate. Avoid using it for memory usage calculations.
Requested by @Gumix in tarantool/tarantool@5a052bd.