Vulkan: StandardMaterial3D specular modes are off by one

[Calinou]

Godot version

4.0.dev (6d98f84)

System information

Fedora 34, GeForce GTX 1080 (NVIDIA 465.31)

Issue description

StandardMaterial3D specular modes are off by one compared to what you configure in the inspector.

From left to right, I configured the spheres to use Toon, Phong, Blinn and SchlickGGX.

However, from left to right, they appear to be Disabled, Toon, Phong, (Blinn or SchlickGGX). There's likely an off-by-one error in the shader since parts of it were removed for performance reasons.

Steps to reproduce

Create StandardMaterial3D, set the albedo to black and tweak the specular mode.

Minimal reproduction project

tests/3d/test_standard_material_3d_opaque.tscn from https://github.com/Calinou/godot-rendering-tests

[clayjohn]

This was fixed at some point! I can't reproduce in RC3