Fix TTL expiration testing documentation

[unboxedtype]

On this page , the test suggests that the call to an expired smart contract will panic. It seems, starting from SDK v.23 this is no longer the case. In the testing environment, the TTL of a contract (and other persistent/instance storage items) will be automatically prolonged once you try to read them.

The test test_persistent_entry_archival() mentioned on the page does no longer exist , it was substituted with another test here that explains the new (quite the opposite, I would say) behavior.