address lints from nightly

[demoray]

tested with cargo 1.78.0-nightly (f772ec022 2024-03-01)

[demoray]

Personally, I don't track nightly. This PR is to address builds failing due to the coverage task being built on nightly.

[vthib]

Ah yes, I use nightly for the coverage to be able to use the #[coverage(off)] directive, which is unstable. There are some activity on the tracking issue, so hopefully it will get stabilized at some point.

The issue is that I have RUSTFLAGS=-Dwarnings set on top of the github actions, so it gets picked up by all jobs. Ideally, this job should not use it, and thus those warnings would not cause the coverage job to fail.

Also, you fixed clippy lints but you didn't really have to, we only do cargo test on nightly.

Thanks for the PR!