### 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)

RS::InstanceType type = RSG::utilities->get_base_type(p_base);
	ERR_FAIL_COND_V(!((1 << type) & RS::INSTANCE_GEOMETRY_MASK), nullptr);
	GeometryInstanceForwardMobile *ginstance = geometry_instance_alloc.alloc();
	ginstance->data = memnew(GeometryInstanceForwardMobile::Data);
	ginstance->data->base = p_base;
	ginstance->data->base_type = type;
	ginstance->data->dependency_tracker.userdata = ginstance;
	ginstance->data->dependency_tracker.changed_callback = _geometry_instance_dependency_changed;
	ginstance->data->dependency_tracker.deleted_callback = _geometry_instance_dependency_deleted;
	ginstance->_mark_dirty();
	return ginstance;
}
void RenderForwardMobile::GeometryInstanceForwardMobile::set_use_lightmap(RID p_lightmap_instance, const Rect2 &p_lightmap_uv_scale, int p_lightmap_slice_index) {
	lightmap_instance = p_lightmap_instance;
	lightmap_uv_scale = p_lightmap_uv_scale;
	lightmap_slice_index = p_lightmap_slice_index;
	_mark_dirty();
}
void RenderForwardMobile::GeometryInstanceForwardMobile::set_lightmap_capture(const Color *p_sh9) {