### Godot version

4.1.1

### System information

windows 11, mobile renderer

### Issue description

On Mobile Vulkan renderer, the clear color is 50% lighter than expected

See steps to reproduce and Minimal reproduction project below.

The box and background have the same color on Forward+ and compatibility, but not on Mobile
happens also in runtime on exported project, not only in editor preview

Images of the same scene from
compatibility:
![compatibility](https://github.com/godotengine/godot/assets/11915378/a874fa86-c16f-43ef-aed7-c2066b770ac1)
Forward+:
![forward](https://github.com/godotengine/godot/assets/11915378/e416f9a6-dfd4-4c47-bbc2-b552ca58f83c)
Mobile:
![mobile](https://github.com/godotengine/godot/assets/11915378/e28e2db8-f7c3-47e2-8c0a-44ce937c9270)


### Steps to reproduce

 - add a CSGBox3D with "unshaded" shading, and albedo of #545454
 - add environment with Background = Custom color and color of #545454

Box and background are not the same color

### Minimal reproduction project

[bg_color.zip](https://github.com/godotengine/godot/files/12174822/bg_color.zip)

m_src = ginstance->data->material_override.is_valid() ? ginstance->data->material_override : p_material;
	SceneShaderForwardMobile::MaterialData *material = nullptr;
	if (m_src.is_valid()) {
		material = static_cast<SceneShaderForwardMobile::MaterialData *>(material_storage->material_get_data(m_src, RendererRD::MaterialStorage::SHADER_TYPE_3D));
		if (!material || !material->shader_data->valid) {
			material = nullptr;
		}
	}
	if (material) {
		if (ginstance->data->dirty_dependencies) {
			material_storage->material_update_dependency(m_src, &ginstance->data->dependency_tracker);
		}
	} else {
		material = static_cast<SceneShaderForwardMobile::MaterialData *>(material_storage->material_get_data(scene_shader.default_material, RendererRD::MaterialStorage::SHADER_TYPE_3D));
		m_src = scene_shader.default_material;
	}
	ERR_FAIL_COND(!material);
	_geometry_instance_add_surface_with_material_chain(ginstance, p_surface, material, m_src, p_mesh);
	if (ginstance->data->material_overlay.is_valid()) {
		m_src = ginstance->data->material_overlay;
		material = static_cast<SceneShaderForwardMobile::MaterialData *>(material_storage->material_get_data(m_src, RendererRD::MaterialStorage::SHADER_TYPE_3D));
		if (material && material->shader_data->valid) {
			if (ginstance->data->dirty_dependencies) {
				material_storage->material_update_dependency(m_src, &ginstance->data->dependency_tracker);
			}
			_geometry_instance_add_surface_with_material_chain(ginstance, p_surface, material, m_src, p_mesh);
		}
	}
}
void RenderForwardMobile::_geometry_instance_update(RenderGeometryInstance *p_geometry_instance) {