Improve sentence

Author: Jaime Terreu

src/ch10-03-lifetime-syntax.md

@@ -44,7 +44,7 @@ The outer scope declares a variable named `r` with no initial value, and the
 inner scope declares a variable named `x` with the initial value of 5. Inside
 the inner scope, we attempt to set the value of `r` as a reference to `x`. Then
 the inner scope ends, and we attempt to print the value in `r`. This code won’t
-compile because the value `r` is referring to has gone out of scope before we
+compile because what the value `r` is referring to has gone out of scope before we
 try to use it. Here is the error message:
 
 ```console