Revise annotations to not refer to subjects as it

listings/ch04-understanding-ownership/no-listing-08-reference-with-annotations/src/main.rs

@@ -9,6 +9,6 @@ fn main() {
 // ANCHOR: here
 fn calculate_length(s: &String) -> usize { // s is a reference to a String
     s.len()
-} // Here, s goes out of scope. But because it does not have ownership of what
-  // it refers to, it is not dropped.
+} // Here, s goes out of scope. But because s does not have ownership of what
+  // it refers to, the value is not dropped.
 // ANCHOR_END: here