Day 1 10.6 Elevator Events code duplication

### Discussed in https://github.com/google/comprehensive-rust/discussions/1525

<div type='discussions-op-text'>

<sup>Originally posted by **ksoo** November 29, 2023</sup>
The code on Day 1 10.6 Elevator Events (https://google.github.io/comprehensive-rust/user-defined-types/exercise.html) seems to be duplicated multiple times. Was there some sort of bug in the generation of this page?</div>