cleaning up memory for array of keys and the node itself when reaching deepest...

cleaning up memory for array of keys and the node itself when reaching deepest point of branch (previous version exposes user to a double-free condition)

slides/cours_22.md

@@ -193,8 +193,6 @@ rien liberer_memoire(page)
     sinon
         pour fille dans page.tab
             liberer_memoire(fille)
-        liberer(page.tab)
-        liberer(page)
 ```
 
 # Les B-arbres