TRPL: minor fixes to the tutorials.

[parir]

r? @steveklabnik

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @steveklabnik (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. The way Github handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see CONTRIBUTING.md for more information.

[Manishearth]

@bors: r+

Could you fix the other errors from #25430 too? Thanks!

[bors]

📌 Commit a499517 has been approved by Manishearth

[bors]

⌛ Testing commit a499517 with merge 4996b8c...

[Manishearth]

@bors: rollup

[bors]

⛄ The build was interrupted to prioritize another pull request.

[parir]

@Manishearth done :)

[Manishearth]

@bors: r+ rollup

[bors]

📌 Commit 94ecc37 has been approved by Manishearth

[bors]

⌛ Testing commit 94ecc37 with merge 13a4b83...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-x-android-t, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-win-32-nopt-t, auto-win-32-opt, auto-win-64-nopt-t, auto-win-64-opt