Minor typo in 6 Data tidying (#1265)

Edited the second code chunk in section 6.3.2 so that pivoted variable names match Figures 6.3, 6.4, and 6.5 for clarity.

data-tidy.qmd

@@ -275,8 +275,8 @@ So we can tidy it with:
 df |> 
   pivot_longer(
     cols = col1:col2,
-    names_to = "names",
-    values_to = "values"
+    names_to = "name",
+    values_to = "value"
   )
 ```