Add "score" as a supported model_type

[ya0guang]

Originally, "score" is not an allowed model type. However, the documentation supports "score" and the method has code related to it. This commit adds it back.

[mcmonkey4eva]

While this code change looks technically correct in and of itself - in actual practice, model_type is always exactly noise, and there is no option to change this in native code.

I marked "Good PR" to give @comfyanonymous final choice on whether to pull or reject. The change is valid, code is correct, "score" is a valid supported model_type input except for this mistaken assert. So it makes code "more correct" but has no actual functional effect. Despite being 7 months old, this PR still applies the same to current comfy code.