* gnu/packages/crates-io.scm (rust-tonic-0.6): Update to 0.6.2. [arguments]: Don't skip build. Skip tests. [cargo-development-inputs]: Add rust-bencher-0.1, rust-quickcheck-1, rust-quickcheck-macros-1, rust-rand-0.8, rust-static-assertions-1, rust-tokio-1, rust-tower-0.4.