message: better way to ignore tests in Miri
diff: @@ -79,13 +79,13 @@ interpreted program or test suite after the second `--`. For example, `cargo
  miri run -- -Zmiri-disable-validation` runs the program without validation of
  basic type invariants and without checking the aliasing of references.
  -When running code via `cargo miri`, the `miri` config flag is set. You can
  -use this to exclude test cases that will fail under Miri because they do things
  +When compiling code via `cargo miri`, the `miri` config flag is set. You can
  +use this to ignore test cases that will fail under Miri because they do things
  Miri does not support:
  ```rust
  -#[cfg(not(miri))]
  #[test]
  +#[cfg_attr(miri, ignore)]
  fn does_not_work_on_miri() {
  std::thread::spawn(|| println!("Hello Thread!"))
  .join()
  