Update 09_day_higher_order_functions.md

Fix a couple of bugs in sample codes.

09_Day_Higher_order_functions/09_day_higher_order_functions.md

@@ -81,7 +81,7 @@ const higherOrder = n => {
     }
     return doWhatEver
   }
-​
+
   return doSomething
 }
 console.log(higherOrder(2)(3)(10))
@@ -212,7 +212,7 @@ console.log(sum)
 ```js
 let sum = 0;
 const numbers = [1,2,3,4,5];
-numbers.forEach(num => sum += num))
+numbers.forEach(num => sum += num)
 
 console.log(sum)
 ```