Update README.md

Removed the insert code snippet as it would be a class exercise.

lectures/10_linked_lists/README.md

@@ -284,13 +284,17 @@ item.
 - If p is a pointer to this node, and x holds the value to be inserted, then the following code will do the insertion.
 Draw a picture to illustrate what is happening.
 
+```cpp
+Class exercise
+```
+<!--
 ```cpp
 Node<T> * q = new Node<T>; // create a new node
 q -> value = x; // store x in this node
 q -> next = p -> next; // make its successor be the current successor of p
 p -> next = q; // make p's successor be this new node
 ```
-
+-->
 - Play this [animation](https://jidongxiao.github.io/CSCI1200-DataStructures/animations/lists/insert/index.html) to see how this code snippet works.
 
 - Note: This code will not work if you want to insert x in a new node at the front of the linked list. Why not?