TextureButton's "normal" state is falsely stated to require a texture

[Meorge]

Your Godot version: 4.3

Issue description: The documentation for TextureButton states the following:

The "normal" state must contain a texture (texture_normal); other textures are optional.

Last night, I was working on a project where I wanted invisible "click zones", and found that TextureButtons worked perfectly fine without me setting any of its textures, including texture_normal.

As such, I think this statement should be removed from the documentation. Before opening a PR to fix it, though, I'd just like to confirm that this is indeed the case, and that there's not some aspect I'm missing. Even if I'm misunderstanding something here, there might be a better way to phrase this sentence in the documentation to better convey what it's trying to convey.

URL to the documentation page: https://docs.godotengine.org/en/stable/classes/class_texturebutton.html