Change cats to cats2

Line 370 - Should be cats2 and not cats, based on the dataset that is being used in the exercise

Author: jsteyn

episodes/04-data-structures-part1.Rmd

@@ -367,7 +367,7 @@ Using the object `cats2`:
 _____
 
 # 2. Show an overview of the table with all data types
-_____(cats)
+_____(cats2)
 
 # 3. The "weight" column has the incorrect data type __________.
 #    The correct data type is: ____________.