clippy aspect won't report "multiple versions for dependency" warnings

I've noticed that `cargo clippy` will report these warnings ([multiple_crate_versions](https://rust-lang.github.io/rust-clippy/master/index.html#multiple_crate_versions)) but `bazel build --config=clippy` will not, even though bazel is in fact building multiple versions of these crates. This means that I still have to run `cargo clippy` instead of `rules_rust`'s `clippy`.