im not sure where support was removed, but it was rather recent, in any case does anyone know why this is?
Removed in version 2017.1.0. A new helper class WebRequestMultimedia has been introduced for simple download of MovieTexture or AudioClip. WebRequest.GetAudioClip() has been deprecated in favor of
Edit: thanks to @Bunny83
The actual direct replacement is WWWAudioExtensions.GetAudioClip. They just wanted to clean up the WWW class and don't have such specific methods inside the WWW class itself.
As you can see in the documentation https://docs.unity3d.com/ScriptReference/WWW-audioClip.html