### Godot version

4.0 Stable

### System information

Ubuntu 22.04

### Issue description

Setting fog_affect_sky = 1 do not have the desired effect when using a Color sky mode. It works properly if we use a procedural sky or the forward+ renderer.

![Screenshot from 2023-03-03 16-50-53](https://user-images.githubusercontent.com/8985409/222870514-0195c4cb-bbca-4e9b-bb6a-6e2a568d2f7b.png)


### Steps to reproduce

Add a sky with a plain color mode like the Clear Color default option. Enable fog and set fog_affect_sky value to 1. Sky is still not affected by fog. 

### Minimal reproduction project
[mobile_fog_sky_bug.zip](https://github.com/godotengine/godot/files/10887265/mobile_fog_sky_bug.zip)


}
	for (uint32_t i = 0; i < MAX_RDL_CULL; i++) {
		uint32_t ofs = i < 4 ? 0 : 1;
		uint32_t shift = (i & 0x3) << 3;
		uint32_t mask = ~(0xFF << shift);
		if (i < p_instance->omni_light_count) {
			p_push_constant->omni_lights[ofs] &= mask;
			p_push_constant->omni_lights[ofs] |= uint32_t(forward_id_allocators[RendererRD::FORWARD_ID_TYPE_OMNI_LIGHT].map[p_instance->omni_lights[i]]) << shift;
		}
		if (i < p_instance->spot_light_count) {
			p_push_constant->spot_lights[ofs] &= mask;
			p_push_constant->spot_lights[ofs] |= uint32_t(forward_id_allocators[RendererRD::FORWARD_ID_TYPE_SPOT_LIGHT].map[p_instance->spot_lights[i]]) << shift;
		}
		if (i < p_instance->decals_count) {
			p_push_constant->decals[ofs] &= mask;
			p_push_constant->decals[ofs] |= uint32_t(forward_id_allocators[RendererRD::FORWARD_ID_TYPE_DECAL].map[p_instance->decals[i]]) << shift;
		}
		if (i < p_instance->reflection_probe_count) {
			p_push_constant->reflection_probes[ofs] &= mask;
			p_push_constant->reflection_probes[ofs] |= uint32_t(forward_id_allocators[RendererRD::FORWARD_ID_TYPE_REFLECTION_PROBE].map[p_instance->reflection_probes[i]]) << shift;
		}
	}
}
void RenderForwardMobile::RenderBufferDataForwardMobile::free_data() {
	
	if (render_buffers) {
		render_buffers->clear_context(RB_SCOPE_MOBILE);
	}
}
void RenderForwardMobile::RenderBufferDataForwardMobile::configure(RenderSceneBuffersRD *p_render_buffers) {