book: Use the expected syntax in the select1 example.

Question: Why did this example work before?

requested review from @Diziet

assigned to @nickm

Question: Why did this example work before?

As per the reference:

The else if between arms is also optional, but else in the fallback clause is mandatory.

Personally I often prefer to omit them, but I have no objection if you'd like to include them here in the book. So please decide what you prefer and then merge or close this.

(Apparently only the abbreviated syntax is shown in the Examples in the reference. Not sure if I want to change that.)

mentioned in commit d75de79d

merged

Decided to merge.

FWIW, I was confused because I looked at the line saying ${if COND1 { ... } else if COND2 { ... } else { ... }} as a description of the syntax, and I didn't expect the syntax to get modified through text later on.