Renaming a struct initializer to match the field name should use shorthand record syntax

I have code like this:

```rust
let inner = unimplemented!();
Item { kind: inner, ..unimplemented!() }
```

When I rename `inner` to `kind`, I expect this to turn into `Item { kind, ..unimplemented!() }`.
Instead, it turns into `Item { kind: kind, ..unimplemented!() }`, and I have to hit ctrl+. again to get the short-hand syntax.