message: tracing: fix link to tracing examples in crate doc
  This fixes the link to the examples in the tracing crate doc.
diff: //! You can find more examples showing how to use this crate [here][examples].
  //!
  //! [RAII]: https://github.com/rust-unofficial/patterns/blob/master/patterns/RAII.md
  -//! [examples]: https://github.com/tokio-rs/tracing/tree/master/tracing/examples
  +//! [examples]: https://github.com/tokio-rs/tracing/tree/master/examples
  //!
  //! ### Events
  //!
  