Update cargo_metadata to v0.15.4 for Rust 2024 support

[m1kc]

This PR updates cargo_metadata to v0.15.4.

Mainly, this allows Cargo.toml files with edition = "2024" to be parsed correctly. With 0.15.3, it just crashes:

$ cargo cache local
thread 'main' (1101299) panicked at /home/m1kc/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/cargo-cache-0.8.3/src/commands/local.rs:93:13:
Failed to parse manifest: 'Cargo.toml'
Error: 'Json(Error("unknown variant `2024`, expected one of `2015`, `2018`, `2021`", line: 1, column: 5101))'
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

(I'm aware that cargo install upgrades package versions by default unless --locked is specified, but that's not the case with cargo binstall and similar tools, which are useful for many reasons aside from their speed.)