AnimationRootNode should be abstract class？

[GitHub7796]

Your Godot version:

4.3

Issue description:

I'm confused about using AnimationTree's AnimationRootNode, I don't know what it does, I looked through the documentation and found that it was a base class, and I didn't think it should be in the following options

URL to the documentation page (if already existing):

https://docs.godotengine.org/en/stable/classes/class_animationrootnode.html

[AThousandShips]

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