message: make sure that we truly do not run no_run doctests
diff: /// assert!(cargo_miri_test::make_true());
  /// ```
  /// ```rust,no_run
  -/// assert!(cargo_miri_test::make_true());
  +/// assert!(!cargo_miri_test::make_true());
  /// ```
  /// ```rust,compile_fail
  /// assert!(cargo_miri_test::make_true() == 5);
  