fix [`manual_unwrap_or_default`] suggestion ignoring side-effects fixes: #12569 closes: #12580 change applicability to `MaybeIncorrect` base on suggestion in [this zulip discussion](https://rust-lang.zulipchat.com/#narrow/stream/257328-clippy/topic/.60manual_unwrap_or_default.60.20suggestion.20removes.20comments) --- changelog: fix [`manual_unwrap_or_default`] suggestion ignoring side-effects, and adjust its applicability.