Ch. 4: Rephrase/clarify paragraph on reference scope (#3688)

Co-authored-by: Chris Krycho <[email protected]>

src/ch04-02-references-and-borrowing.md

@@ -173,8 +173,8 @@ reading of the data.
 
 Note that a reference’s scope starts from where it is introduced and continues
 through the last time that reference is used. For instance, this code will
-compile because the last usage of the immutable references, the `println!`,
-occurs before the mutable reference is introduced:
+compile because the last usage of the immutable references is in the `println!`,
+before the mutable reference is introduced:
 
 ```rust,edition2021
 {{#rustdoc_include ../listings/ch04-understanding-ownership/no-listing-13-reference-scope-ends/src/main.rs:here}}