FontVariation.variation_transform mentions incorrect Transform2D constructor

**Your Godot version:** 4.x stable

**Issue description:**
The page for `FontVariation` uses a `Transform2D` constructor that is not exposed to scripts:

> `Transform2D variation_transform = Transform2D(1, 0, 0, 1, 0, 0)`

> For example, to simulate italic typeface by slanting, apply the following transform `Transform2D(1.0, slant, 0.0, 1.0, 0.0, 0.0)`.

**URL to the documentation page:**
https://docs.godotengine.org/en/stable/classes/class_fontvariation.html#class-fontvariation-property-variation-transform
https://docs.godotengine.org/en/stable/classes/class_transform2d.html#constructors

I'm not sure whether it's considered correct to change the default assignment along with the example in the description, though it would certainly help those less familiar with transform matrices.