Idiomatic: Various minor tweaks to doc comments section

[randomPoison]

Various minor tweaks to the "Meaningful Doc Comments" section of Idiomatic based on my experience teaching the class for the first time.

• Fix a few formatting issues in speaker notes that caused the markdown to not render cleanly.
• Trim a few speaker notes that I think are redundant.
• anatomy-of-a-doc-comment.md - Reorder speaker note so the Q&A about panics is organized under the section about panics.
• what-why-not-how-where.md - Remove the sort_quickly example. This is later used as the example in the exercise, and I think discussing it before the exercise undercuts the value of the exercise.