message: fix another colon->semi-colon typo
diff: @@ -86,7 +86,7 @@ Let's go back and walk through that benchmark code in more detail.
  ```rust
  #[macro_use]
  extern crate criterion;
  -extern crate mycrate:
  +extern crate mycrate;
  use criterion::Criterion;
  use criterion::black_box;
  