rust.inc: remove unused var and now not-so-useful comments
rust.inc: remove unused var and now not-so-useful comments

cardoe/meta-rust,jmesmon/meta-rust,cardoe/meta-rust,cardoe/meta-rust,meta-rust/meta-rust,jmesmon/meta-rust,meta-rust/meta-rust,jmesmon/meta-rust,starlab-io/meta-rust,cardoe/meta-rust,meta-rust/meta-rust,jmesmon/meta-rust,starlab-io/meta-rust,meta-rust/meta-rust,meta-rust/meta-rust