The publish-lockfile option is not usable

[phil-opp]

The publish-lockfile manifest key was introduced in #5093 as a nightly feature. However, it is not usable at the moment because nightly-only features are not allowed on crates.io:

> cargo publish
error: cannot publish crates which activate nightly-only cargo features to crates.io

cc @alexcrichton

[oli-obk]

The same goes for cargo-features = ["edition"], which means that there will be no more published clippy versions until this issue is resolved