Inconsistent 'missing `new`' warnings

Consider this sample:
```fsharp
open System

type AsyncDisposable() =
interface IAsyncDisposable with
member this.DisposeAsync() = failwith "todo"

type Disposable() =
interface IDisposable with
member this.Dispose() = failwith "todo"

AsyncDisposable() |> ignore
Disposable() |> ignore
```

There's an inconsistency in how different kinds of disposables are checked in terms of requiring `new` keyword. I think we both interfaces should probably be treated equally: