message: docs: correct grammar in README
diff: @@ -243,7 +243,7 @@ my_future
  `Future::instrument` attaches a span to the future, ensuring that the span's lifetime
  is as long as the future's.
  -Under the hood, the [`#[instrument]`][instrument] macro performs same the explicit span
  +Under the hood, the [`#[instrument]`][instrument] macro performs the same explicit span
  attachment that `Future::instrument` does.
  [std-future]: https://doc.rust-lang.org/stable/std/future/trait.Future.html
  