chore: 🔥 remove last R code chunk so Quarto doesn't need to use R (#44)

## Description

Now that the last R code chunk is removed, we can render the website
without that dependency.

Closes #39

## Reviewer Focus

This PR needs a quick review. 

## Checklist

- [x] Ran spell-check
- [x] Formatted Markdown
- [x] Rendered website locally

sessions/lesson.qmd

@@ -2,10 +2,6 @@
 
 {{< include ../includes/_wip.qmd >}}
 
-```{r setup}
-#| include: false
-```
-
 <!-- TODO: Add an introduction here -->
 
 **Session objectives**:
@@ -22,12 +18,6 @@ TODO: Reading text
 
 > Time: \## minutes.
 
-```{r solution-LABEL}
-#| eval: false
-#| code-fold: true
-#| code-summary: "**Click for the solution**. Only click if you are struggling or are out of time."
-```
-
 ## Summary
 
 -   TODO: List of summary items