Outdated text in "Creating Operators" subsection of book

[lucasdu2]

In this section of the book, I got lost for a bit and I believe it's due to the fact the example was updated but not synced with the explanatory text. In particular, this relatively recent commit updated the actual example, but the corresponding explanation has not been updated since this commit from 6 years ago.

[frankmcsherry]

Thanks for the call out! We'll take a peek.