Show what use_field_init_shorthand = true does

It did not include `b` for the `use_field_init_shorthand = true` case,
which is a mistake as it is the one thing that will be changed by this
option.

Author: bernardosulzbach

Configurations.md

@@ -3046,6 +3046,7 @@ fn main() {
     let y = 2;
     let z = 3;
     let a = Foo { x, y, z };
+    let b = Foo { x, y, z };
 }
 ```