Do not set up wrong span for adjustments

tests/ui/codemap_tests/issue-11715.stderr

@@ -7,7 +7,7 @@ LL |     let z = &mut x;
    |             ^^^^^^ second mutable borrow occurs here
 LL |     z.use_mut();
 LL |     y.use_mut();
-   |     ----------- first borrow later used here
+   |     - first borrow later used here
 
 error: aborting due to previous error
 

tests/ui/codemap_tests/one_line.stderr

@@ -2,9 +2,8 @@ error[E0499]: cannot borrow `v` as mutable more than once at a time
   --> $DIR/one_line.rs:3:12
    |
 LL |     v.push(v.pop().unwrap());
-   |     -------^^^^^^^----------
-   |     | |    |
-   |     | |    second mutable borrow occurs here
+   |     - ---- ^ second mutable borrow occurs here
+   |     | |
    |     | first borrow later used by call
    |     first mutable borrow occurs here
    |