docs(shoppingsummarycounter): fix indentation

subjects/shoppingsummarycounter/README.md

@@ -22,15 +22,15 @@ Here is a possible program to test your function:
 package main
 
 import (
-  "fmt"
-  "piscine"
+        "fmt"
+        "piscine"
 )
 
 func main() {
-  summary := "Burger Water Carrot Coffee Water Water Chips Carrot Carrot Burger Carrot Water"
-    for index,element := range piscine.ShoppingSummaryCounter(summary){
-      fmt.Println(index,"=>",element)
-    }
+        summary := "Burger Water Carrot Coffee Water Water Chips Carrot Carrot Burger Carrot Water"
+        for index, element := range piscine.ShoppingSummaryCounter(summary) {
+          fmt.Println(index,"=>",element)
+        }
 }
 ```