Address some clippy lints

[m17rt] / tools / m17rt-soundcards / Cargo.toml

[package]
name = "m17rt-soundcards"
version = "0.1.0"
edition = "2021"
license = "MIT"
authors = ["Thomas Karpiniec <tom.karpiniec@outlook.com"]
publish = false

[dependencies]
m17app = { path = "../../m17app" }