Remove Dead Domains

[celenityy]

I probably also need to start clearing out dead domains. I generally only try to add domains that are active/I stumble across, but I'm sure some inactive ones are still slipping through the cracks. Goal is to keep these lists as efficient & effective as possible, so no reason to include anything dead or not actively being used.

AdGuard's DeadDomainsLinter looks promising for this, will have to investigate and try out when I'm able to get around to it.