Fix typo in task 40's documentation

Author: jschear

src/v_builders/_40_BuildersHowItWorks.kt

@@ -7,7 +7,7 @@ fun todoTask40(): Nothing = TODO(
     """
         Task 40.
         Look at the questions below and give your answers:
-        change 'insertAnswerHere()' in task26's map to your choice (a, b or c).
+        change 'insertAnswerHere()' in task40's map to your choice (a, b or c).
 
         All the constants are imported via 'util.questions.Answer.*', so they can be accessed by name.