[Buildbot-status]Windows 8.1 worker (bolen-windows8) retirement

My Windows 8.1 worker got hit on Wednesday by some "encrypt the world" ransomware. I'm not quite sure the path by which it reached the Azure VM, but regardless, it's toast.

I don't think I see enough value in re-installation, given the existence of the Windows 10 worker, plus I can probably bump some Windows 10 worker resources with the budget freed up by Windows 8. So I'm planning on letting the Windows 8 worker end its run at this point.

-- David