Merge branch 'radhwan.hassine-master-patch-53145' into 'master'

Update cours_9.md

See merge request algorithmique/cours!57

slides/cours_9.md

@@ -327,8 +327,8 @@ int stack_pop(stack *s) {
 . . .
 
 ```C
-int stack_peek(stack *s) {
-    return s->data[s->top];
+int stack_peek(stack s) {
+    return s.data[s.top];
 }
 ```