Mention about libc-test on the publishing note

CONTRIBUTING.md

@@ -69,11 +69,11 @@ platform in this crate, the next step is to get that sweet, sweet usage from
 crates.io! The only next step is to bump the version of libc and then publish
 it. If you'd like to get a release out ASAP you can follow these steps:
 
-1. Increment the patch version number in `Cargo.toml`.
-1. Send a PR to this repository. It should [look like this][example], but it'd
+1. Increment the patch version number in `Cargo.toml` and `libc-test/Cargo.toml`.
+1. Send a PR to this repository. It should [look like this][example-pr], but it'd
    also be nice to fill out the description with a small rationale for the
    release (any rationale is ok though!)
 1. Once merged, the release will be tagged and published by one of the libc crate
    maintainers.
 
-[example]: https://github.com/rust-lang/libc/pull/583
+[example-pr]: https://github.com/rust-lang/libc/pull/2120