MODEL_MATRIX is a non-functioning fragment built-in #12418

Your Godot version: 4.7.1.stable.official

Issue description:
When working with a spatial shader, MODEL_MATRIX is available in fragment().
The value of MODEL_MATRIX in fragment() appears to be an identity matrix rather than the actual transform as found in vertex()

URL to the documentation page:
https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/spatial_shader.html#fragment-built-ins

This should either be removed from the fragment built-ins, or updated to carry the correct value. I'm not sure which is appropriate.