Change range to 10

Co-authored-by: Dustin J. Mitchell <[email protected]>

src/iterators/helpers.md

@@ -9,7 +9,7 @@ In addition to the `next` method that defines how an iterator behaves, the
 customized iterators.
 
 ```rust,editable
-let result: i32 = (1..10) // Create a range from 1 to 9
+let result: i32 = (1..=10) // Create a range from 1 to 10
     .filter(|&x| x % 2 == 0) // Keep only even numbers
     .map(|x| x * x) // Square each number
     .sum(); // Sum up all the squared numbers