RequiresExplicitTypeArguments always results in warnings when applied to functions with no explicit type arguments

Consider the following F# code:

```fsharp
[]
let f x = x

f 12 |> ignore
```

This gives an error:

```
The generic function 'f' must be given explicit type argument(s)
```

So I can give it a type argument, like `int` or `_`:

```fsharp
[]
let f x = x

f 12 |> ignore
f<_> "hello" |> ignore
```

But I get a new warning:

```
The method or function 'f' should not be given explicit type argument(s) because it does not
declare its type parameters explicitly
```

Giving it a type argument satisfies that warning (but I can't do the last line anymore since it's now been specialized to `int`).

I think it should instead give a warning on the attribute application if there isn't an explicit type parameters.