Such policies would be incredibly unpopular, so you would need a true tyrant to make it happen. And even then, genetic editing would be a very expensive and slow option compared to just regular forms of oppression. Can that tyrant keep power for the decades it will take for them to get their subservient work-force?

It seems very unlikely that poorer countries with dictators would have the skilled workforce, competence, and resources to pull this off. Perhaps some wealthy authoritarian states like the UAE could do it, but it would still require a massive effort for it to happen. And why bother when they can just import labour instead?