Obsolete attribute is ignored in constructor property assignment

Given code like
```fs
    System.Text.Json.JsonSerializerOptions(
                    JsonSerializerDefaults.Web,
                    IgnoreNullValues = true)
```

`IgnoreNullValues` is obsolete but does not trigger a warning.

Writing `System.Text.Json.JsonSerializerOptions().IgnoreNullValues` does properly warn.
