Wrong description about world position

**Your Godot version:** 3.5.1

**Issue description:**

> In Godot, all transform math is done relative to the parent node. When we refer to "world position", that would be relative to the node's parent instead, if the node had a parent.

World position is not relative to the node's parent. It's relative to its first ancestor Node2D/Node3D/Control node. I'm not sure how to describe it clearly, also when plain nodes / top level nodes are involved. For example:

* Viewport
* Node2D
* AnimationPlayer
* Node2D - global position uses the same coordinate as this node
* Node2D
* CurrentNode2D

**URL to the documentation page:**

https://docs.godotengine.org/en/stable/tutorials/math/matrices_and_transforms.html
https://docs.godotengine.org/en/latest/tutorials/math/matrices_and_transforms.html