Exercise timing too short - Ep02: mapping a mental model

### What is the problem?

5 minutes are given for this, but 10 is more realistic

### Location of problem (optional)

https://carpentries.github.io/instructor-training/instructor/02-practice-learning.html#mapping-a-mental-model

Open the linked “Mapping a mental model” lesson section and locate its source in the repository. Update the exercise timing from 5 minutes to 10 minutes, then check the rendered lesson to confirm the revised duration is shown correctly.

Written by the indexing model from the issue text.