message: docs: update README.md
  Update the closing-spans link.
diff: @@ -249,7 +249,7 @@ attachment that `Future::instrument` does.
  [std-future]: https://doc.rust-lang.org/stable/std/future/trait.Future.html
  [`tracing-futures`]: https://docs.rs/tracing-futures
  -[closing]: https://docs.rs/tracing/latest/span/index.html#closing-spans
  +[closing]: https://docs.rs/tracing/latest/tracing/span/index.html#closing-spans
  [`Future::instrument`]: https://docs.rs/tracing/latest/tracing/trait.Instrument.html#method.instrument
  [`#[instrument]`]: https://docs.rs/tracing/0.1.11/tracing/attr.instrument.html
  