"Run this code" should be "compile this code" (ch18-03-pattern-syntax)

[Tanja-4732]

Compile errors/warnings occur during compile-time, not during runtime.

I recommend the following change in chapter 18.3:

Is:

In Listing 18-20, we create two unused variables, but when we run this code, we should only get a warning about one of them.

Should be:

In Listing 18-20, we create two unused variables, but when we compile this code, we should only get a warning about one of them.

Or should be:

In Listing 18-20, we create two unused variables, but when we build this code, we should only get a warning about one of them.