Allow dead code to avoid warning

[Bi0T1N]

Without it the compiler generates following warning:

warning: variant `Fahrenheit` is never constructed

[rustbot]

Failed to set assignee to marioidival: cannot assign: HTTP status client error (403 Forbidden) for url (https://api.github.com/repos/rust-lang/rust-by-example/issues/1688/assignees)

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[rustbot]

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

[marioidival]

Nice, but can I suggest something? Can you add some example to fill the gap instead of remove the warning?

[Bi0T1N]

As far as I understood the user should change the line let temperature = Temperature::Celsius(35); and test different numbers as well as using let temperature = Temperature::Fahrenheit(35);. For the latter one the compiler will bark at Temperature::Celsius because it is dead code then.