Callback example fix

although the function does square, we called it callBack

09_Day/09_day_higher_order_functions.md

@@ -63,7 +63,7 @@ function cube(callback, n) {
   return callback(n) * n
 }
 ​
-console.log(cube(square, 3))
+console.log(cube(callBack, 3))
 ```
 
 ### Returning function
@@ -581,4 +581,4 @@ console.log(users); // sorted ascending
 
 🎉 CONGRATULATIONS ! 🎉
   
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+[<< Day 8](https://github.com/Asabeneh/30DaysOfJavaScript/blob/master/08_Day/08_day_objects.md) | [Day 10 >>](#)