msxml3/tests: Mark Win10 behaviour as broken

[Nikolay Sivov]

On 04.01.2017 18:49, André Hentschel wrote:
>      V_VT(&varbody_ref) = VT_VARIANT|VT_BYREF;
>      V_VARIANTREF(&varbody_ref) = &varbody;
>      hr = IXMLHttpRequest_send(xhr, varbody_ref);
> -    EXPECT_HR(hr, S_OK);
> +    ok(hr == S_OK || broken(hr == E_INVALIDARG) /* win10 */, "got 0x%08x, expected S_OK or E_INVALIDARG\n", hr);

I don't think this has any value without understanding why it fails.