remove unused deps

[kingosticks]

I think there are more than this but these stood out to me, and I caused one of them (rpassword).

[yubiuser]

There might be even more...

/workspaces/librespot # cargo machete
Analyzing dependencies of crates in this directory...
cargo-machete found the following unused dependencies in this directory:
librespot-protocol -- ./protocol/Cargo.toml:
        protobuf
librespot -- ./Cargo.toml:
        rpassword
        webpki
librespot-discovery -- ./discovery/Cargo.toml:
        cfg-if
librespot-audio -- ./audio/Cargo.toml:
        byteorder
        futures-core
librespot-metadata -- ./metadata/Cargo.toml:
        byteorder
librespot-playback -- ./playback/Cargo.toml:
        byteorder
        glib
        

[kingosticks]

If you try removing protobuf from librespot-protocol it doesn't end very well. That tool is limited. But the others look sensible and seems to build.