message: tracing: Fix link to RAII pattern document
  ## Motivation
  The RAII pattern documentation has been moved.
  ## Solution
  Update the link to the document.
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
  +//! [RAII]: https://github.com/rust-unofficial/patterns/blob/master/patterns/behavioural/RAII.md
  //! [examples]: https://github.com/tokio-rs/tracing/tree/master/examples
  //!
  //! ### Events
  