### 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)

if (ginstance->data->cast_double_sided_shadows) {
		flags |= GeometryInstanceSurfaceDataCache::FLAG_USES_DOUBLE_SIDED_SHADOWS;
	}
	if (has_alpha || p_material->shader_data->depth_draw == SceneShaderForwardMobile::ShaderData::DEPTH_DRAW_DISABLED || p_material->shader_data->depth_test == SceneShaderForwardMobile::ShaderData::DEPTH_TEST_DISABLED) {
		
		flags |= GeometryInstanceSurfaceDataCache::FLAG_PASS_ALPHA;
		if ((p_material->shader_data->uses_depth_prepass_alpha || p_material->shader_data->uses_alpha_antialiasing) && !(p_material->shader_data->depth_draw == SceneShaderForwardMobile::ShaderData::DEPTH_DRAW_DISABLED || p_material->shader_data->depth_test == SceneShaderForwardMobile::ShaderData::DEPTH_TEST_DISABLED)) {
			flags |= GeometryInstanceSurfaceDataCache::FLAG_PASS_DEPTH;
			flags |= GeometryInstanceSurfaceDataCache::FLAG_PASS_SHADOW;
		}
	} else {
		flags |= GeometryInstanceSurfaceDataCache::FLAG_PASS_OPAQUE;
		flags |= GeometryInstanceSurfaceDataCache::FLAG_PASS_DEPTH;
		flags |= GeometryInstanceSurfaceDataCache::FLAG_PASS_SHADOW;
	}
	if (p_material->shader_data->uses_particle_trails) {
		flags |= GeometryInstanceSurfaceDataCache::FLAG_USES_PARTICLE_TRAILS;
	}
	SceneShaderForwardMobile::MaterialData *material_shadow = nullptr;
	void *surface_shadow = nullptr;
	if (!p_material->shader_data->uses_particle_trails && !p_material->shader_data->writes_modelview_or_projection && !p_material->shader_data->uses_vertex && !p_material->shader_data->uses_discard && !p_material->shader_data->uses_depth_prepass_alpha && !p_material->shader_data->uses_alpha_clip && !p_material->shader_data->uses_alpha_antialiasing) {
		flags |= GeometryInstanceSurfaceDataCache::FLAG_USES_SHARED_SHADOW_MATERIAL;
		material_shadow = static_cast<SceneShaderForwardMobile::MaterialData *>(RendererRD::MaterialStorage::get_singleton()->material_get_data(scene_shader.default_material, RendererRD::MaterialStorage::SHADER_TYPE_3D));
		RID shadow_mesh = mesh_storage->mesh_get_shadow_mesh(p_mesh);
		if (shadow_mesh.is_valid()) {
			surface_shadow = mesh_storage->mesh_get_surface(shadow_mesh, p_surface);
		}
	} else {
		material_shadow = p_material;
	}