Update 03-basics-factors-dataframes.Rmd

Fix typo

episodes/03-basics-factors-dataframes.Rmd

@@ -263,7 +263,7 @@ Ok, thats a lot up unpack! Some things to notice.
   ```
 
   This result makes sense because `mode()` (which deals with how an object is stored)
-  tells us that `variants` treated as a **list** in R. A data frame is in some sense a "fancy" list.
+  tells us that `variants` is treated as a **list** in R. A data frame is in some sense a "fancy" list.
   However, data fames do have some specific properties beyond that of a basic list, so they have their own
   class (**data.frame**), which is important for functions (and programmers) to know.
   :::::::::::::::::::::::::